diff --git a/core/config/schema/core.data_types.schema.yml b/core/config/schema/core.data_types.schema.yml
index 41332e3..f9bf353 100644
--- a/core/config/schema/core.data_types.schema.yml
+++ b/core/config/schema/core.data_types.schema.yml
@@ -118,7 +118,7 @@ action_configuration_default:
   type: sequence
   label: 'Action configuration'
   sequence:
-    - type: string
+    type: string
 
 theme_settings:
   type: mapping
@@ -181,13 +181,13 @@ theme_settings:
       type: sequence
       label: 'Third party settings'
       sequence:
-        - type: theme_settings.third_party.[%key]
+        type: theme_settings.third_party.[%key]
 
 theme_breakpoints_default:
   type: sequence
   sequence:
-    - type: string
-      label: 'Breakpoint value'
+    type: string
+    label: 'Breakpoint value'
 
 views_field_bulk_form:
   type: views_field
@@ -203,8 +203,8 @@ views_field_bulk_form:
       type: sequence
       label: 'Available actions'
       sequence:
-        - type: string
-          label: 'Action'
+        type: string
+        label: 'Action'
 
 # Array of routes with route_name and route_params keys.
 route:
@@ -218,8 +218,8 @@ route:
       type: sequence
       label: 'Route Params'
       sequence:
-        - type: string
-          label: 'Param'
+        type: string
+        label: 'Param'
 
 # Config dependencies.
 config_dependencies_base:
@@ -229,22 +229,22 @@ config_dependencies_base:
       type: sequence
       label: 'Configuration entity dependencies'
       sequence:
-        - type: string
+        type: string
     content:
       type: sequence
       label: 'Content entity dependencies'
       sequence:
-        - type: string
+        type: string
     module:
       type: sequence
       label: 'Module dependencies'
       sequence:
-        - type: string
+        type: string
     theme:
       type: sequence
       label: 'Theme dependencies'
       sequence:
-        - type: string
+        type: string
 
 config_dependencies:
   type: config_dependencies_base
@@ -273,7 +273,7 @@ config_entity:
       type: sequence
       label: 'Third party settings'
       sequence:
-        - type: '[%parent.%parent.%type].third_party.[%key]'
+        type: '[%parent.%parent.%type].third_party.[%key]'
 
 block_settings:
   type: mapping
@@ -299,8 +299,8 @@ block_settings:
           type: sequence
           label: 'Vary by context'
           sequence:
-            - type: string
-              label: 'Context'
+            type: string
+            label: 'Context'
     status:
       type: boolean
       label: 'Status'
@@ -331,7 +331,7 @@ condition.plugin:
       type: sequence
       label: 'Context assignments'
       sequence:
-        - type: string
+        type: string
 
 display_variant.plugin:
   type: mapping
@@ -391,8 +391,8 @@ field_config_base:
       type: sequence
       label: 'Default values'
       sequence:
-        - type: field.value.[%parent.%parent.field_type]
-          label: 'Default value'
+        type: field.value.[%parent.%parent.field_type]
+        label: 'Default value'
     default_value_callback:
       type: string
       label: 'Default value callback'
@@ -614,8 +614,8 @@ field.field_settings.email:
   type: mapping
   label: 'Email settings'
   sequence:
-    - type: string
-      label: 'Setting'
+    type: string
+    label: 'Setting'
 
 field.value.email:
   type: mapping
diff --git a/core/config/schema/core.entity.schema.yml b/core/config/schema/core.entity.schema.yml
index aa26f9a..423acb7 100644
--- a/core/config/schema/core.entity.schema.yml
+++ b/core/config/schema/core.entity.schema.yml
@@ -55,32 +55,32 @@ core.entity_view_display.*.*.*:
       type: sequence
       label: 'Field formatters'
       sequence:
-        - type: mapping
-          label: 'Field formatter'
-          mapping:
-            type:
-              type: string
-              label: 'Format type machine name'
-            weight:
-              type: integer
-              label: 'Weight'
-            label:
-               type: string
-               label: 'Label setting machine name'
-            settings:
-              type: field.formatter.settings.[%parent.type]
-              label: 'Settings'
-            third_party_settings:
-               type: sequence
-               label: 'Third party settings'
-               sequence:
-                 - type: field.formatter.third_party.[%key]
+        type: mapping
+        label: 'Field formatter'
+        mapping:
+          type:
+            type: string
+            label: 'Format type machine name'
+          weight:
+            type: integer
+            label: 'Weight'
+          label:
+             type: string
+             label: 'Label setting machine name'
+          settings:
+            type: field.formatter.settings.[%parent.type]
+            label: 'Settings'
+          third_party_settings:
+             type: sequence
+             label: 'Third party settings'
+             sequence:
+               type: field.formatter.third_party.[%key]
     hidden:
       type: sequence
       label: 'Field display setting'
       sequence:
-        - type: boolean
-          label: 'Value'
+        type: boolean
+        label: 'Value'
 
 # Overview configuration information for form mode displays.
 core.entity_form_display.*.*.*:
@@ -106,29 +106,29 @@ core.entity_form_display.*.*.*:
       type: sequence
       label: 'Field widgets'
       sequence:
-        - type: mapping
-          label: 'Field widget'
-          mapping:
-            type:
-              type: string
-              label: 'Widget type machine name'
-            weight:
-              type: integer
-              label: 'Weight'
-            settings:
-              type: field.widget.settings.[%parent.type]
-              label: 'Settings'
-            third_party_settings:
-              type: sequence
-              label: 'Third party settings'
-              sequence:
-                - type: field.widget.third_party.[%key]
+        type: mapping
+        label: 'Field widget'
+        mapping:
+          type:
+            type: string
+            label: 'Widget type machine name'
+          weight:
+            type: integer
+            label: 'Weight'
+          settings:
+            type: field.widget.settings.[%parent.type]
+            label: 'Settings'
+          third_party_settings:
+            type: sequence
+            label: 'Third party settings'
+            sequence:
+              type: field.widget.third_party.[%key]
     hidden:
       type: sequence
       label: 'Hidden'
       sequence:
-        - type: boolean
-          label: 'Component'
+        type: boolean
+        label: 'Component'
 
 # Default schema for entity display field with undefined type.
 field.formatter.settings.*:
diff --git a/core/config/schema/core.extension.schema.yml b/core/config/schema/core.extension.schema.yml
index 1d09eeb..f53e5e6 100644
--- a/core/config/schema/core.extension.schema.yml
+++ b/core/config/schema/core.extension.schema.yml
@@ -6,11 +6,11 @@ core.extension:
       type: sequence
       label: 'Enabled modules'
       sequence:
-        - type: integer
-          label: 'Weight'
+        type: integer
+        label: 'Weight'
     theme:
       type: sequence
       label: 'Installed themes'
       sequence:
-        - type: integer
-          label: 'Weight'
+        type: integer
+        label: 'Weight'
diff --git a/core/config/schema/core.menu.schema.yml b/core/config/schema/core.menu.schema.yml
index ac11b46..069ec19 100644
--- a/core/config/schema/core.menu.schema.yml
+++ b/core/config/schema/core.menu.schema.yml
@@ -6,21 +6,21 @@ core.menu.static_menu_link_overrides:
       type: sequence
       label: Definitions
       sequence:
-        - type: mapping
-          label: Definition
-          mapping:
-            menu_name:
-              type: string
-              label: 'Menu name'
-            parent:
-              type: string
-              label: 'Parent'
-            weight:
-              type: integer
-              label: 'Weight'
-            expanded:
-              type: boolean
-              label: 'Expanded'
-            enabled:
-              type: boolean
-              label: 'Enabled'
+        type: mapping
+        label: Definition
+        mapping:
+          menu_name:
+            type: string
+            label: 'Menu name'
+          parent:
+            type: string
+            label: 'Parent'
+          weight:
+            type: integer
+            label: 'Weight'
+          expanded:
+            type: boolean
+            label: 'Expanded'
+          enabled:
+            type: boolean
+            label: 'Enabled'
diff --git a/core/lib/Drupal/Core/Config/Schema/Sequence.php b/core/lib/Drupal/Core/Config/Schema/Sequence.php
index b7c34c2..01312d2 100644
--- a/core/lib/Drupal/Core/Config/Schema/Sequence.php
+++ b/core/lib/Drupal/Core/Config/Schema/Sequence.php
@@ -23,7 +23,8 @@ class Sequence extends ArrayElement {
    */
   protected function getElementDefinition($key) {
     $value = isset($this->value[$key]) ? $this->value[$key] : NULL;
-    $definition = isset($this->definition['sequence'][0]) ? $this->definition['sequence'][0] : array();
+    // @todo: Remove BC layer for sequence with hyphen in front. https://www.drupal.org/node/2444979
+    $definition = isset($this->definition['sequence'][0]) ? $this->definition['sequence'][0] : (isset($this->definition['sequence']) ? $this->definition['sequence'] : array());
     return $this->buildDataDefinition($definition, $value, $key);
   }
 
diff --git a/core/modules/aggregator/config/schema/aggregator.schema.yml b/core/modules/aggregator/config/schema/aggregator.schema.yml
index db7c93a6..97b3d3f 100644
--- a/core/modules/aggregator/config/schema/aggregator.schema.yml
+++ b/core/modules/aggregator/config/schema/aggregator.schema.yml
@@ -14,8 +14,8 @@ aggregator.settings:
       type: sequence
       label: 'Processors'
       sequence:
-        - type: string
-          label: 'Processor'
+        type: string
+        label: 'Processor'
     items:
       type: mapping
       label: 'Items'
diff --git a/core/modules/block/config/schema/block.schema.yml b/core/modules/block/config/schema/block.schema.yml
index 1e6b823..16d79bc 100644
--- a/core/modules/block/config/schema/block.schema.yml
+++ b/core/modules/block/config/schema/block.schema.yml
@@ -28,8 +28,8 @@ block.block.*:
       type: sequence
       label: 'Visibility Conditions'
       sequence:
-        - type: condition.plugin.[id]
-          label: 'Visibility Condition'
+        type: condition.plugin.[id]
+        label: 'Visibility Condition'
 
 block.settings.*:
   type: block_settings
diff --git a/core/modules/book/config/schema/book.schema.yml b/core/modules/book/config/schema/book.schema.yml
index 20d18bc..c9fb1bf 100644
--- a/core/modules/book/config/schema/book.schema.yml
+++ b/core/modules/book/config/schema/book.schema.yml
@@ -8,8 +8,8 @@ book.settings:
       type: sequence
       label: 'Content types allowed in book outlines'
       sequence:
-        - type: string
-          label: 'Content type'
+        type: string
+        label: 'Content type'
     block:
       type: mapping
       label: 'Block'
diff --git a/core/modules/ckeditor/config/schema/ckeditor.schema.yml b/core/modules/ckeditor/config/schema/ckeditor.schema.yml
index 0ac8c41..f38d2f6 100644
--- a/core/modules/ckeditor/config/schema/ckeditor.schema.yml
+++ b/core/modules/ckeditor/config/schema/ckeditor.schema.yml
@@ -12,26 +12,26 @@ editor.settings.ckeditor:
           type: sequence
           label: 'Rows'
           sequence:
-            - type: sequence
-              label: 'Button groups'
-              sequence:
-                - type: mapping
-                  label: 'Button group'
-                  mapping:
-                    name:
-                      type: string
-                      label: 'Button group name'
-                    items:
-                      type: sequence
-                      label: 'Buttons'
-                      sequence:
-                        - type: string
-                          label: 'Button'
+            type: sequence
+            label: 'Button groups'
+            sequence:
+              type: mapping
+              label: 'Button group'
+              mapping:
+                name:
+                  type: string
+                  label: 'Button group name'
+                items:
+                  type: sequence
+                  label: 'Buttons'
+                  sequence:
+                    type: string
+                    label: 'Button'
     plugins:
       type: sequence
       label: 'Plugins'
       sequence:
-        - type: ckeditor.plugin.[%key]
+        type: ckeditor.plugin.[%key]
 
 # Plugin \Drupal\ckeditor\Plugin\ckeditor\plugin\StylesCombo
 ckeditor.plugin.stylescombo:
diff --git a/core/modules/color/config/schema/color.schema.yml b/core/modules/color/config/schema/color.schema.yml
index 4b81f0c..008148c 100644
--- a/core/modules/color/config/schema/color.schema.yml
+++ b/core/modules/color/config/schema/color.schema.yml
@@ -6,15 +6,15 @@ color.theme.*:
       type: sequence
       label: 'Palette settings'
       sequence:
-        - type: color_hex
+        type: color_hex
     logo:
       type: path
       label: 'Logo path'
     stylesheets:
       type: sequence
       sequence:
-        - type: path
+        type: path
     files:
       type: sequence
       sequence:
-        - type: path
+        type: path
diff --git a/core/modules/comment/config/schema/comment.schema.yml b/core/modules/comment/config/schema/comment.schema.yml
index 9dd0aa5..d9f5a77 100644
--- a/core/modules/comment/config/schema/comment.schema.yml
+++ b/core/modules/comment/config/schema/comment.schema.yml
@@ -28,8 +28,8 @@ action.configuration.comment_unpublish_by_keyword_action:
       type: sequence
       label: 'Keywords'
       sequence:
-        - type: string
-          label: 'Keyword'
+        type: string
+        label: 'Keyword'
 
 action.configuration.comment_unpublish_action:
   type: action_configuration_default
diff --git a/core/modules/config/src/Tests/ConfigSchemaTest.php b/core/modules/config/src/Tests/ConfigSchemaTest.php
index 2bbfee5..37adff0 100644
--- a/core/modules/config/src/Tests/ConfigSchemaTest.php
+++ b/core/modules/config/src/Tests/ConfigSchemaTest.php
@@ -165,14 +165,14 @@ function testSchemaMapping() {
     $expected['mapping']['label']['type'] = 'label';
     $expected['mapping']['label']['label'] = 'Label';
     $expected['mapping']['effects']['type'] = 'sequence';
-    $expected['mapping']['effects']['sequence'][0]['type'] = 'mapping';
-    $expected['mapping']['effects']['sequence'][0]['mapping']['id']['type'] = 'string';
-    $expected['mapping']['effects']['sequence'][0]['mapping']['data']['type'] = 'image.effect.[%parent.id]';
-    $expected['mapping']['effects']['sequence'][0]['mapping']['weight']['type'] = 'integer';
-    $expected['mapping']['effects']['sequence'][0]['mapping']['uuid']['type'] = 'string';
+    $expected['mapping']['effects']['sequence']['type'] = 'mapping';
+    $expected['mapping']['effects']['sequence']['mapping']['id']['type'] = 'string';
+    $expected['mapping']['effects']['sequence']['mapping']['data']['type'] = 'image.effect.[%parent.id]';
+    $expected['mapping']['effects']['sequence']['mapping']['weight']['type'] = 'integer';
+    $expected['mapping']['effects']['sequence']['mapping']['uuid']['type'] = 'string';
     $expected['mapping']['third_party_settings']['type'] = 'sequence';
     $expected['mapping']['third_party_settings']['label'] = 'Third party settings';
-    $expected['mapping']['third_party_settings']['sequence'][0]['type'] = '[%parent.%parent.%type].third_party.[%key]';
+    $expected['mapping']['third_party_settings']['sequence']['type'] = '[%parent.%parent.%type].third_party.[%key]';
     $expected['type'] = 'image.style.*';
 
     $this->assertEqual($definition, $expected);
@@ -343,6 +343,7 @@ public function testConfigSaveWithSchema() {
       'float' => '3.14',
       'null_float' => '',
       'sequence' => array (1, 0, 1),
+      'sequence_bc' => array(1, 0, 1),
       // Not in schema and therefore should be left untouched.
       'not_present_in_schema' => TRUE,
       // Test a custom type.
@@ -365,6 +366,7 @@ public function testConfigSaveWithSchema() {
       'float' => 3.14,
       'null_float' => NULL,
       'sequence' => array (TRUE, FALSE, TRUE),
+      'sequence_bc' => array(TRUE, FALSE, TRUE),
       'not_present_in_schema' => TRUE,
       'config_schema_test_integer' => 1,
       'config_schema_test_integer_empty_string' => NULL,
diff --git a/core/modules/config/tests/config_schema_test/config/schema/config_schema_test.schema.yml b/core/modules/config/tests/config_schema_test/config/schema/config_schema_test.schema.yml
index 8c8660c..6b4f62d 100644
--- a/core/modules/config/tests/config_schema_test/config/schema/config_schema_test.schema.yml
+++ b/core/modules/config/tests/config_schema_test/config/schema/config_schema_test.schema.yml
@@ -119,6 +119,10 @@ config_schema_test.schema_data_types:
     sequence:
       type: sequence
       sequence:
+        type: boolean
+    sequence_bc:
+      type: sequence
+      sequence:
         - type: boolean
 
 config_schema_test.schema_in_install:
@@ -156,16 +160,16 @@ config_schema_test.plugin_types:
     tests:
       type: sequence
       sequence:
-        - type: test.plugin_types.[plugin_id]
+        type: test.plugin_types.[plugin_id]
     test_with_parents:
       type: sequence
       sequence:
-        - type: mapping
-          mapping:
-            plugin_id:
-              type: string
-            settings:
-              type: test_with_parents.plugin_types.[%parent.plugin_id]
+        type: mapping
+        mapping:
+          plugin_id:
+            type: string
+          settings:
+            type: test_with_parents.plugin_types.[%parent.plugin_id]
 
 test.plugin_types:
   type: mapping
diff --git a/core/modules/config/tests/config_test/config/schema/config_test.schema.yml b/core/modules/config/tests/config_test/config/schema/config_test.schema.yml
index 9240d4b..1657750 100644
--- a/core/modules/config/tests/config_test/config/schema/config_test.schema.yml
+++ b/core/modules/config/tests/config_test/config/schema/config_test.schema.yml
@@ -40,11 +40,11 @@ config_test.query.*:
       type: sequence
       label: 'Array level 1'
       sequence:
-        - type: sequence
-          label: 'Array level 2'
-          sequence:
-            - type: integer
-              label: 'Value'
+        type: sequence
+        label: 'Array level 2'
+        sequence:
+          type: integer
+          label: 'Value'
     number:
       type: integer
       label: 'number'
@@ -57,8 +57,8 @@ config_test.types:
       type: sequence
       label: 'Array'
       sequence:
-        - type: string
-          label: 'Item'
+        type: string
+        label: 'Item'
     boolean:
       type: boolean
       label: 'Boolean'
diff --git a/core/modules/config_translation/tests/modules/config_translation_test/config/schema/config_translation_test.schema.yml b/core/modules/config_translation/tests/modules/config_translation_test/config/schema/config_translation_test.schema.yml
index 4e43d5f..a5ff2e6 100644
--- a/core/modules/config_translation/tests/modules/config_translation_test/config/schema/config_translation_test.schema.yml
+++ b/core/modules/config_translation/tests/modules/config_translation_test/config/schema/config_translation_test.schema.yml
@@ -20,5 +20,5 @@ config_translation_test.content:
       type: sequence
       label: 'Animals'
       sequence:
-        - type: label
+        type: label
 
diff --git a/core/modules/contact/config/schema/contact.schema.yml b/core/modules/contact/config/schema/contact.schema.yml
index 7ebb6f4..080a9c8 100644
--- a/core/modules/contact/config/schema/contact.schema.yml
+++ b/core/modules/contact/config/schema/contact.schema.yml
@@ -14,8 +14,8 @@ contact.form.*:
       type: sequence
       label: 'Recipients'
       sequence:
-        - type: email
-          label: 'Email address'
+        type: email
+        label: 'Email address'
     reply:
       type: text
       label: 'Auto-reply'
diff --git a/core/modules/content_translation/config/schema/content_translation.schema.yml b/core/modules/content_translation/config/schema/content_translation.schema.yml
index ddccb5b..808a6e7 100644
--- a/core/modules/content_translation/config/schema/content_translation.schema.yml
+++ b/core/modules/content_translation/config/schema/content_translation.schema.yml
@@ -8,8 +8,8 @@ field.field.*.*.*.third_party.content_translation:
       type: sequence
       label: 'Field properties for which to synchronize translations'
       sequence:
-        - type: string
-          label: 'Field column for which to synchronize translations'
+        type: string
+        label: 'Field column for which to synchronize translations'
 
 language.content_settings.*.*.third_party.content_translation:
   type: mapping
diff --git a/core/modules/contextual/config/schema/contextual.views.schema.yml b/core/modules/contextual/config/schema/contextual.views.schema.yml
index 235ada5..4be573c 100644
--- a/core/modules/contextual/config/schema/contextual.views.schema.yml
+++ b/core/modules/contextual/config/schema/contextual.views.schema.yml
@@ -8,8 +8,8 @@ views.field.contextual_links:
       type: sequence
       label: 'Fields'
       sequence:
-        - type: string
-          label: 'Link'
+        type: string
+        label: 'Link'
     destination:
       type: boolean
       label: 'Include destination'
diff --git a/core/modules/entity_reference/config/schema/entity_reference.schema.yml b/core/modules/entity_reference/config/schema/entity_reference.schema.yml
index ec291fa..d244bec 100644
--- a/core/modules/entity_reference/config/schema/entity_reference.schema.yml
+++ b/core/modules/entity_reference/config/schema/entity_reference.schema.yml
@@ -8,8 +8,8 @@ entity_reference.default.handler_settings:
       type: sequence
       label: 'types'
       sequence:
-        - type: string
-          label: 'Type'
+        type: string
+        label: 'Type'
     sort:
       type: mapping
       label: 'Sort settings'
@@ -31,8 +31,8 @@ entity_reference.default.handler_settings:
           type: sequence
           label: 'Restrict to the selected roles'
           sequence:
-            - type: string
-              label: 'Role'
+            type: string
+            label: 'Role'
     auto_create:
       type: boolean
       label: 'Create referenced entities if they don''t already exist'
diff --git a/core/modules/entity_reference/config/schema/entity_reference.views.schema.yml b/core/modules/entity_reference/config/schema/entity_reference.views.schema.yml
index f92af7b..2660e53 100644
--- a/core/modules/entity_reference/config/schema/entity_reference.views.schema.yml
+++ b/core/modules/entity_reference/config/schema/entity_reference.views.schema.yml
@@ -16,5 +16,5 @@ views.style.entity_reference:
       type: sequence
       label: 'Search fields'
       sequence:
-        - type: string
-          label: 'Search field'
+        type: string
+        label: 'Search field'
diff --git a/core/modules/field/config/schema/field.schema.yml b/core/modules/field/config/schema/field.schema.yml
index 429c929..9ea9b2e 100644
--- a/core/modules/field/config/schema/field.schema.yml
+++ b/core/modules/field/config/schema/field.schema.yml
@@ -42,11 +42,11 @@ field.storage.*.*:
       type: sequence
       label: 'Indexes'
       sequence:
-        - type: sequence
-          label: 'Indexes'
-          sequence:
-            - type: ignore
-              label: 'Index'
+        type: sequence
+        label: 'Indexes'
+        sequence:
+          type: ignore
+          label: 'Index'
     persist_with_no_fields:
       type: boolean
       label: 'Persist field storage with no fields'
diff --git a/core/modules/field/config/schema/field.views.schema.yml b/core/modules/field/config/schema/field.views.schema.yml
index 85c501f..bdef72e 100644
--- a/core/modules/field/config/schema/field.views.schema.yml
+++ b/core/modules/field/config/schema/field.views.schema.yml
@@ -36,8 +36,8 @@ views.field.field:
       type: sequence
       label: 'Group by columns'
       sequence:
-        - type: string
-          label: 'Column'
+        type: string
+        label: 'Column'
     group_rows:
       type: boolean
       label: 'Display all values in the same row'
diff --git a/core/modules/filter/config/schema/filter.schema.yml b/core/modules/filter/config/schema/filter.schema.yml
index 6a28b4e..ac956f7 100644
--- a/core/modules/filter/config/schema/filter.schema.yml
+++ b/core/modules/filter/config/schema/filter.schema.yml
@@ -28,13 +28,13 @@ filter.format.*:
       type: sequence
       label: 'Roles'
       sequence:
-        - type: string
-          label: 'Role'
+        type: string
+        label: 'Role'
     filters:
       type: sequence
       label: 'Enabled filters'
       sequence:
-        - type: filter
+        type: filter
     langcode:
       type: string
       label: 'Default language'
@@ -46,8 +46,8 @@ filter_settings.*:
   type: sequence
   label: 'Filter settings'
   sequence:
-    - type: string
-      label: 'Value'
+    type: string
+    label: 'Value'
 
 filter_settings.filter_html:
   type: filter
diff --git a/core/modules/filter/tests/filter_test/config/schema/filter_test.schema.yml b/core/modules/filter/tests/filter_test/config/schema/filter_test.schema.yml
index eb07f18..53fd4a3 100644
--- a/core/modules/filter/tests/filter_test/config/schema/filter_test.schema.yml
+++ b/core/modules/filter/tests/filter_test/config/schema/filter_test.schema.yml
@@ -12,11 +12,11 @@ filter_settings.filter_test_restrict_tags_and_attributes:
           type: sequence
           label: 'Allowed tags and attributes'
           sequence:
-            - type: ignore
-              label: 'Tag and optionally list of attributes'
+            type: ignore
+            label: 'Tag and optionally list of attributes'
         forbidden_tags:
           type: sequence
           label: 'Forbidden tags'
           sequence:
-            - type: boolean
-              label: 'Tag'
+            type: boolean
+            label: 'Tag'
diff --git a/core/modules/forum/config/schema/forum.schema.yml b/core/modules/forum/config/schema/forum.schema.yml
index f74587c..2e01710 100644
--- a/core/modules/forum/config/schema/forum.schema.yml
+++ b/core/modules/forum/config/schema/forum.schema.yml
@@ -47,7 +47,7 @@ block.settings.forum_active_block:
       type: sequence
       label: 'Properties'
       sequence:
-        - type: string
+        type: string
     block_count:
       type: integer
       label: 'Block count'
@@ -60,7 +60,7 @@ block.settings.forum_new_block:
       type: sequence
       label: 'Properties'
       sequence:
-        - type: string
+        type: string
     block_count:
       type: integer
       label: 'Block count'
diff --git a/core/modules/image/config/schema/image.schema.yml b/core/modules/image/config/schema/image.schema.yml
index 00268ef..41dbb98 100644
--- a/core/modules/image/config/schema/image.schema.yml
+++ b/core/modules/image/config/schema/image.schema.yml
@@ -12,16 +12,16 @@ image.style.*:
     effects:
       type: sequence
       sequence:
-        - type: mapping
-          mapping:
-            id:
-              type: string
-            data:
-              type: image.effect.[%parent.id]
-            weight:
-              type: integer
-            uuid:
-              type: string
+        type: mapping
+        mapping:
+          id:
+            type: string
+          data:
+            type: image.effect.[%parent.id]
+          weight:
+            type: integer
+          uuid:
+            type: string
 
 image.effect.*:
   type: mapping
diff --git a/core/modules/language/config/schema/language.schema.yml b/core/modules/language/config/schema/language.schema.yml
index bd03869..6c082e1 100644
--- a/core/modules/language/config/schema/language.schema.yml
+++ b/core/modules/language/config/schema/language.schema.yml
@@ -8,14 +8,14 @@ language_type_negotiation:
       type: sequence
       label: 'Enabled negotiators'
       sequence:
-        - type: integer
-          label: Weight
+        type: integer
+        label: Weight
     method_weights:
       type: sequence
       label: 'Negotiator weights'
       sequence:
-        - type: integer
-          label: Weight
+        type: integer
+        label: Weight
 
 language.types:
   type: mapping
@@ -25,20 +25,20 @@ language.types:
       type: sequence
       label: 'All language types'
       sequence:
-        - type: string
-          label: 'Language type'
+        type: string
+        label: 'Language type'
     configurable:
       type: sequence
       label: 'Configurable language types'
       sequence:
-        - type: string
-          label: 'Language type'
+        type: string
+        label: 'Language type'
     negotiation:
       type: sequence
       label: 'Language negotiation per type settings'
       sequence:
-        - type: language_type_negotiation
-          label: 'Language negotiation per type setting'
+        type: language_type_negotiation
+        label: 'Language negotiation per type setting'
 
 language.negotiation:
   type: mapping
@@ -62,14 +62,14 @@ language.negotiation:
           type: sequence
           label: 'Path prefix configuration'
           sequence:
-            - type: string
-              label: 'Path prefix'
+            type: string
+            label: 'Path prefix'
         domains:
           type: sequence
           label: 'Domain configuration'
           sequence:
-            - type: string
-              label: 'Domain'
+            type: string
+            label: 'Domain'
     selected_langcode:
       type: string
       label: 'Selected language'
@@ -78,8 +78,8 @@ language.mappings:
   type: sequence
   label: 'Language mapping'
   sequence:
-    - type: string
-      label: 'Language'
+    type: string
+    label: 'Language'
 
 language.entity.*:
   type: config_entity
@@ -127,4 +127,4 @@ condition.plugin.language:
     langcodes:
       type: sequence
       sequence:
-        - type: string
+        type: string
diff --git a/core/modules/link/config/schema/link.schema.yml b/core/modules/link/config/schema/link.schema.yml
index 7983652..4c25a8f 100644
--- a/core/modules/link/config/schema/link.schema.yml
+++ b/core/modules/link/config/schema/link.schema.yml
@@ -68,7 +68,7 @@ field.value.link:
           type: sequence
           label: 'Url query key value pairs'
           sequence:
-            - type: string
+            type: string
         fragment:
           type: string
           label: 'Url fragment'
@@ -82,4 +82,4 @@ field.value.link:
           type: sequence
           label: 'Link attributes'
           sequence:
-            - type: string
+            type: string
diff --git a/core/modules/menu_ui/config/schema/menu_ui.schema.yml b/core/modules/menu_ui/config/schema/menu_ui.schema.yml
index ad096f2..19d3efc 100644
--- a/core/modules/menu_ui/config/schema/menu_ui.schema.yml
+++ b/core/modules/menu_ui/config/schema/menu_ui.schema.yml
@@ -16,8 +16,8 @@ node.type.*.third_party.menu_ui:
       type: sequence
       label: 'Available menus'
       sequence:
-       - type: string
-         label: 'Menu machine name'
+       type: string
+       label: 'Menu machine name'
     parent:
       type: string
       label: 'Parent'
diff --git a/core/modules/migrate/config/schema/migrate.schema.yml b/core/modules/migrate/config/schema/migrate.schema.yml
index fe4ea1a..c48bdd1 100644
--- a/core/modules/migrate/config/schema/migrate.schema.yml
+++ b/core/modules/migrate/config/schema/migrate.schema.yml
@@ -11,8 +11,8 @@ migrate.migration.*:
       type: sequence
       label: 'Migration Groups'
       sequence:
-        - type: string
-          label: 'Group'
+        type: string
+        label: 'Group'
     label:
       type: label
       label: 'Label'
@@ -36,11 +36,11 @@ migrate.migration.*:
           type: sequence
           label: 'Required dependencies'
           sequence:
-            - type: string
-              label: 'Dependency'
+            type: string
+            label: 'Dependency'
         optional:
           type: sequence
           label: 'Optional dependencies'
           sequence:
-            - type: string
-              label: 'Dependency'
+            type: string
+            label: 'Dependency'
diff --git a/core/modules/migrate_drupal/config/schema/migrate_drupal.source.schema.yml b/core/modules/migrate_drupal/config/schema/migrate_drupal.source.schema.yml
index e28173f..e43ffe8 100644
--- a/core/modules/migrate_drupal/config/schema/migrate_drupal.source.schema.yml
+++ b/core/modules/migrate_drupal/config/schema/migrate_drupal.source.schema.yml
@@ -8,8 +8,8 @@ migrate.source.variable:
       type: sequence
       label: 'Variables'
       sequence:
-        - type: string
-          label: 'Variable'
+        type: string
+        label: 'Variable'
     constants:
       type: mapping
       label: 'Constants'
@@ -132,8 +132,8 @@ migrate.source.variable_multirow:
       type: sequence
       label: 'Variables'
       sequence:
-        - type: string
-          label: 'Variable'
+        type: string
+        label: 'Variable'
 
 migrate.source.d6_comment_variable:
   type: migrate_source_sql
@@ -151,8 +151,8 @@ migrate.source.d6_contact_settings:
       type: sequence
       label: 'Variables'
       sequence:
-        - type: string
-          label: 'Variable'
+        type: string
+        label: 'Variable'
 
 migrate.source.d6_view_mode:
   type: migrate_source_sql
@@ -303,8 +303,8 @@ migrate_entity_constant:
       type: sequence
       label: 'Empty'
       sequence:
-        - type: string
-          label: 'Empty'
+        type: string
+        label: 'Empty'
     name:
       type: string
       label: 'Name'
@@ -333,14 +333,14 @@ migrate_entity_constant:
       type: sequence
       label: 'Settings'
       sequence:
-        - type: ignore
-          label: 'Settings'
+        type: ignore
+        label: 'Settings'
     settings:
       type: sequence
       label: 'Settings'
       sequence:
-        - type: ignore
-          label: 'Settings'
+        type: ignore
+        label: 'Settings'
     options:
       type: mapping
       label: 'Options'
@@ -358,5 +358,5 @@ migrate_entity_constant:
           type: sequence
           label: 'Settings'
           sequence:
-            - type: string
-              label: 'Settings'
+            type: string
+            label: 'Settings'
diff --git a/core/modules/node/config/schema/node.schema.yml b/core/modules/node/config/schema/node.schema.yml
index 9b8931c..3ec6c8e 100644
--- a/core/modules/node/config/schema/node.schema.yml
+++ b/core/modules/node/config/schema/node.schema.yml
@@ -43,8 +43,8 @@ search.plugin.node_search:
       type: sequence
       label: 'Content ranking'
       sequence:
-        - type: integer
-          label: 'Influence'
+        type: integer
+        label: 'Influence'
 
 action.configuration.node_assign_owner_action:
   type: mapping
@@ -94,8 +94,8 @@ action.configuration.node_unpublish_by_keyword_action:
       type: sequence
       label: 'Keywords'
       sequence:
-        - type: string
-          label: 'Keyword'
+        type: string
+        label: 'Keyword'
 
 block.settings.node_syndicate_block:
   type: block_settings
@@ -111,4 +111,4 @@ condition.plugin.node_type:
     bundles:
       type: sequence
       sequence:
-        - type: string
+        type: string
diff --git a/core/modules/node/config/schema/node.views.schema.yml b/core/modules/node/config/schema/node.views.schema.yml
index b1d24d9..f8fd8c7 100644
--- a/core/modules/node/config/schema/node.views.schema.yml
+++ b/core/modules/node/config/schema/node.views.schema.yml
@@ -70,8 +70,8 @@ views.argument_default.node:
   type: sequence
   label: 'Content ID from URL'
   sequence:
-    - type: string
-      label: 'Nid'
+    type: string
+    label: 'Nid'
 
 views.argument_validator.node:
   type: mapping
@@ -81,8 +81,8 @@ views.argument_validator.node:
       type: sequence
       label: 'Content types'
       sequence:
-        - type: string
-          label: 'Type'
+        type: string
+        label: 'Type'
     access:
       type: boolean
       label: 'Validate user has access to the content'
@@ -204,8 +204,8 @@ views.filter.node_uid_revision:
       type: sequence
       label: 'Values'
       sequence:
-        - type: string
-          label: 'Value'
+        type: string
+        label: 'Value'
     expose:
       type: mapping
       label: 'Expose'
diff --git a/core/modules/options/config/schema/options.schema.yml b/core/modules/options/config/schema/options.schema.yml
index 7bd7547..017b396 100644
--- a/core/modules/options/config/schema/options.schema.yml
+++ b/core/modules/options/config/schema/options.schema.yml
@@ -8,15 +8,15 @@ field.storage_settings.list_integer:
       type: sequence
       label: 'Allowed values list'
       sequence:
-        - type: mapping
-          label: 'Allowed value with label'
-          mapping:
-            value:
-              type: integer
-              label: 'Value'
-            label:
-              type: label
-              label: 'Label'
+        type: mapping
+        label: 'Allowed value with label'
+        mapping:
+          value:
+            type: integer
+            label: 'Value'
+          label:
+            type: label
+            label: 'Label'
     allowed_values_function:
       type: string
       label: 'Allowed values function'
@@ -41,15 +41,15 @@ field.storage_settings.list_float:
       type: sequence
       label: 'Allowed values list'
       sequence:
-        - type: mapping
-          label: 'Allowed value with label'
-          mapping:
-            value:
-              type: float
-              label: 'Value'
-            label:
-              type: label
-              label: 'Label'
+        type: mapping
+        label: 'Allowed value with label'
+        mapping:
+          value:
+            type: float
+            label: 'Value'
+          label:
+            type: label
+            label: 'Label'
     allowed_values_function:
       type: string
       label: 'Allowed values function'
@@ -74,15 +74,15 @@ field.storage_settings.list_string:
       type: sequence
       label: 'Allowed values list'
       sequence:
-        - type: mapping
-          label: 'Allowed value with label'
-          mapping:
-            value:
-              type: string
-              label: 'Value'
-            label:
-              type: label
-              label: 'Label'
+        type: mapping
+        label: 'Allowed value with label'
+        mapping:
+          value:
+            type: string
+            label: 'Value'
+          label:
+            type: label
+            label: 'Label'
     allowed_values_function:
       type: string
       label: 'Allowed values function'
diff --git a/core/modules/rdf/config/schema/rdf.data_types.schema.yml b/core/modules/rdf/config/schema/rdf.data_types.schema.yml
index ef35469..f2f83f7 100644
--- a/core/modules/rdf/config/schema/rdf.data_types.schema.yml
+++ b/core/modules/rdf/config/schema/rdf.data_types.schema.yml
@@ -6,7 +6,7 @@ rdf_field_mapping:
       type: sequence
       label: 'Properties'
       sequence:
-        - type: string
+        type: string
     datatype:
       type: string
       label: 'Data type'
diff --git a/core/modules/rdf/config/schema/rdf.schema.yml b/core/modules/rdf/config/schema/rdf.schema.yml
index ac452a3..a331382 100644
--- a/core/modules/rdf/config/schema/rdf.schema.yml
+++ b/core/modules/rdf/config/schema/rdf.schema.yml
@@ -17,9 +17,9 @@ rdf.mapping.*.*:
       type: sequence
       label: 'Types'
       sequence:
-        - type: string
+        type: string
     fieldMappings:
       type: sequence
       label: 'Field mappings'
       sequence:
-        - type: rdf_field_mapping
+        type: rdf_field_mapping
diff --git a/core/modules/responsive_image/config/schema/responsive_image.schema.yml b/core/modules/responsive_image/config/schema/responsive_image.schema.yml
index fb3b9a0..f9f0162 100644
--- a/core/modules/responsive_image/config/schema/responsive_image.schema.yml
+++ b/core/modules/responsive_image/config/schema/responsive_image.schema.yml
@@ -14,23 +14,23 @@ responsive_image.styles.*:
       type: sequence
       label: 'Image style mappings'
       sequence:
-        - type: mapping
-          label: 'Image style mapping'
-          mapping:
-            # Image mapping type. Either 'sizes' (using the 'sizes' attribute)
-            # or 'image_style' (using a single image style to map to this
-            # breakpoint).
-            image_mapping_type:
-              type: string
-              label: 'Responsive image mapping type'
-            image_mapping:
-              type: responsive_image.image_mapping_type.[%parent.image_mapping_type]
-            breakpoint_id:
-              type: string
-              label: 'Breakpoint ID'
-            multiplier:
-              type: string
-              label: 'Multiplier'
+        type: mapping
+        label: 'Image style mapping'
+        mapping:
+          # Image mapping type. Either 'sizes' (using the 'sizes' attribute)
+          # or 'image_style' (using a single image style to map to this
+          # breakpoint).
+          image_mapping_type:
+            type: string
+            label: 'Responsive image mapping type'
+          image_mapping:
+            type: responsive_image.image_mapping_type.[%parent.image_mapping_type]
+          breakpoint_id:
+            type: string
+            label: 'Breakpoint ID'
+          multiplier:
+            type: string
+            label: 'Multiplier'
     breakpoint_group:
       type: string
       label: 'Breakpoint group'
@@ -51,8 +51,8 @@ responsive_image.image_mapping_type.sizes:
       type: sequence
       label: 'Image styles to be used when using the ''sizes'' attribute'
       sequence:
-        - type: string
-          label: 'Image style'
+        type: string
+        label: 'Image style'
 
 field.formatter.settings.responsive_image:
   type: mapping
diff --git a/core/modules/rest/config/schema/rest.schema.yml b/core/modules/rest/config/schema/rest.schema.yml
index b9cb652..21952ae 100644
--- a/core/modules/rest/config/schema/rest.schema.yml
+++ b/core/modules/rest/config/schema/rest.schema.yml
@@ -8,8 +8,8 @@ rest.settings:
       type: sequence
       label: 'Resources'
       sequence:
-        - type: rest_resource
-          label: 'Resource'
+        type: rest_resource
+        label: 'Resource'
 
 rest_resource:
   type: mapping
@@ -34,11 +34,11 @@ rest_request:
       type: sequence
       label: 'Supported format'
       sequence:
-        - type: string
-          label: 'Format'
+        type: string
+        label: 'Format'
     supported_auth:
       type: sequence
       label: 'Supported authentication'
       sequence:
-        - type: string
-          label: 'Authentication'
+        type: string
+        label: 'Authentication'
diff --git a/core/modules/rest/config/schema/rest.views.schema.yml b/core/modules/rest/config/schema/rest.views.schema.yml
index 00a7589..a914081 100644
--- a/core/modules/rest/config/schema/rest.views.schema.yml
+++ b/core/modules/rest/config/schema/rest.views.schema.yml
@@ -12,15 +12,15 @@ views.row.data_field:
       type: sequence
       label: 'Options'
       sequence:
-        - type: mapping
-          label: 'Row'
-          mapping:
-            alias:
-              type: string
-              label: 'Alias for ID'
-            raw_output:
-              type: boolean
-              label: 'Raw output for ID'
+        type: mapping
+        label: 'Row'
+        mapping:
+          alias:
+            type: string
+            label: 'Alias for ID'
+          raw_output:
+            type: boolean
+            label: 'Raw output for ID'
 
 views.style.serializer:
   type: views_style
@@ -30,5 +30,5 @@ views.style.serializer:
       type: sequence
       label: 'Formats'
       sequence:
-        - type: string
-          label: 'Format'
+        type: string
+        label: 'Format'
diff --git a/core/modules/system/config/schema/system.schema.yml b/core/modules/system/config/schema/system.schema.yml
index a8d13fa..6888a56 100644
--- a/core/modules/system/config/schema/system.schema.yml
+++ b/core/modules/system/config/schema/system.schema.yml
@@ -140,8 +140,8 @@ system.filter:
       type: sequence
       label: 'Allowed protocols'
       sequence:
-        - type: string
-          label: 'Protocol'
+        type: string
+        label: 'Protocol'
 
 system.logging:
   type: mapping
@@ -333,8 +333,8 @@ system.mail:
       type: sequence
       label: 'Interfaces'
       sequence:
-        - type: string
-          label: 'Interface'
+        type: string
+        label: 'Interface'
 
 system.theme.global:
   type: theme_settings
diff --git a/core/modules/taxonomy/config/schema/taxonomy.schema.yml b/core/modules/taxonomy/config/schema/taxonomy.schema.yml
index c79fa5f..79703eb 100644
--- a/core/modules/taxonomy/config/schema/taxonomy.schema.yml
+++ b/core/modules/taxonomy/config/schema/taxonomy.schema.yml
@@ -45,15 +45,15 @@ field.storage_settings.taxonomy_term_reference:
       type: sequence
       label: 'Allowed values'
       sequence:
-        - type: mapping
-          label: 'Allowed values'
-          mapping:
-            vocabulary:
-              type: string
-              label: 'Vocabulary'
-            parent:
-              type: integer
-              value: 'Parent'
+        type: mapping
+        label: 'Allowed values'
+        mapping:
+          vocabulary:
+            type: string
+            label: 'Vocabulary'
+          parent:
+            type: integer
+            value: 'Parent'
 
 field.field_settings.taxonomy_term_reference:
   type: mapping
diff --git a/core/modules/taxonomy/config/schema/taxonomy.views.schema.yml b/core/modules/taxonomy/config/schema/taxonomy.views.schema.yml
index d64639e..9bda788 100644
--- a/core/modules/taxonomy/config/schema/taxonomy.views.schema.yml
+++ b/core/modules/taxonomy/config/schema/taxonomy.views.schema.yml
@@ -57,8 +57,8 @@ views.argument_validator.taxonomy_term_name:
       type: sequence
       label: 'Vocabularies'
       sequence:
-        - type: string
-          label: 'Vocabulary'
+        type: string
+        label: 'Vocabulary'
 
 views.argument_default.taxonomy_tid:
   type: mapping
@@ -77,8 +77,8 @@ views.argument_default.taxonomy_tid:
       type: sequence
       label: 'Vocabularies'
       sequence:
-        - type: string
-          label: 'Vocabulary'
+        type: string
+        label: 'Vocabulary'
     anyall:
       type: string
       label: 'Multiple-value handling'
@@ -126,8 +126,8 @@ views.field.taxonomy_index_tid:
       type: sequence
       label: 'Vocabularies'
       sequence:
-        - type: string
-          label: 'Vocabulary'
+        type: string
+        label: 'Vocabulary'
 
 views.filter.taxonomy_index_tid:
   type: views.filter.many_to_one
@@ -152,8 +152,8 @@ views.filter.taxonomy_index_tid:
       type: sequence
       label: 'Values'
       sequence:
-        - type: integer
-          label: 'Value'
+        type: integer
+        label: 'Value'
 
 views.filter.taxonomy_index_tid_depth:
   type: views.filter.taxonomy_index_tid
@@ -171,5 +171,5 @@ views.relationship.node_term_data:
       type: sequence
       label: 'Vocabularies'
       sequence:
-        - type: string
-          label: 'Vocabulary'
+        type: string
+        label: 'Vocabulary'
diff --git a/core/modules/tour/config/schema/tour.schema.yml b/core/modules/tour/config/schema/tour.schema.yml
index 5d0d85e..caf7363 100644
--- a/core/modules/tour/config/schema/tour.schema.yml
+++ b/core/modules/tour/config/schema/tour.schema.yml
@@ -17,14 +17,14 @@ tour.tour.*:
       type: sequence
       label: 'Route settings'
       sequence:
-        - type: route
-          label: 'Route'
+        type: route
+        label: 'Route'
     tips:
       type: sequence
       label: 'Tips'
       sequence:
-        - type: tour.tip.[plugin]
-          label: 'Tour tip'
+        type: tour.tip.[plugin]
+        label: 'Tour tip'
 
 tour.tip:
   type: mapping
@@ -49,8 +49,8 @@ tour.tip:
       type: sequence
       label: 'Attributes'
       sequence:
-        - type: string
-          label: 'Attribute'
+        type: string
+        label: 'Attribute'
 
 tour.tip.text:
   type: tour.tip
diff --git a/core/modules/update/config/schema/update.schema.yml b/core/modules/update/config/schema/update.schema.yml
index 43421ec..ee1924a 100644
--- a/core/modules/update/config/schema/update.schema.yml
+++ b/core/modules/update/config/schema/update.schema.yml
@@ -35,8 +35,8 @@ update.settings:
           type: sequence
           label: 'Email addresses to notify when updates are available'
           sequence:
-            - type: email
-              label: 'Email'
+            type: email
+            label: 'Email'
         threshold:
           type: string
           label: 'Email notification threshold'
diff --git a/core/modules/update/tests/modules/update_test/config/schema/update_test.schema.yml b/core/modules/update/tests/modules/update_test/config/schema/update_test.schema.yml
index 55f7ec8..69a84b7 100644
--- a/core/modules/update/tests/modules/update_test/config/schema/update_test.schema.yml
+++ b/core/modules/update/tests/modules/update_test/config/schema/update_test.schema.yml
@@ -8,24 +8,24 @@ update_test.settings:
       type: sequence
       label: 'System info'
       sequence:
-        - type: sequence
-          label: 'Items'
-          sequence:
-            - type: string
-              label: 'Item'
+        type: sequence
+        label: 'Items'
+        sequence:
+          type: string
+          label: 'Item'
     update_status:
       type: sequence
       label: 'Update status'
       sequence:
-        - type: mapping
-          label: 'Module'
-          mapping:
-            status:
-              type: integer
-              label: 'Value'
+        type: mapping
+        label: 'Module'
+        mapping:
+          status:
+            type: integer
+            label: 'Value'
     xml_map:
       type: sequence
       label: 'XML map'
       sequence:
-        - type: string
-          label: 'Value'
+        type: string
+        label: 'Value'
diff --git a/core/modules/user/config/schema/user.schema.yml b/core/modules/user/config/schema/user.schema.yml
index 772deea..d7ad693 100644
--- a/core/modules/user/config/schema/user.schema.yml
+++ b/core/modules/user/config/schema/user.schema.yml
@@ -132,8 +132,8 @@ user.role.*:
       type: sequence
       label: 'Permissions'
       sequence:
-        - type: string
-          label: 'Permission'
+        type: string
+        label: 'Permission'
 
 action.configuration.user_add_role_action:
   type: mapping
@@ -173,4 +173,4 @@ condition.plugin.user_role:
     roles:
       type: sequence
       sequence:
-        - type: string
+        type: string
diff --git a/core/modules/user/config/schema/user.views.schema.yml b/core/modules/user/config/schema/user.views.schema.yml
index e1b83f3..6a84b18 100644
--- a/core/modules/user/config/schema/user.views.schema.yml
+++ b/core/modules/user/config/schema/user.views.schema.yml
@@ -16,8 +16,8 @@ views.access.role:
       type: sequence
       label: 'List of roles'
       sequence:
-        - type: string
-          label: 'Role'
+        type: string
+        label: 'Role'
 
 views.argument.user_uid:
   type: views.argument.numeric
@@ -41,8 +41,8 @@ views.argument_validator.user:
       type: sequence
       label: 'Restrict to the selected roles'
       sequence:
-        - type: string
-          label: 'Role'
+        type: string
+        label: 'Role'
 
 views.argument_default.user:
   type: mapping
diff --git a/core/modules/views/config/schema/views.argument_validator.schema.yml b/core/modules/views/config/schema/views.argument_validator.schema.yml
index 6e3cb44..af1ebfd 100644
--- a/core/modules/views/config/schema/views.argument_validator.schema.yml
+++ b/core/modules/views/config/schema/views.argument_validator.schema.yml
@@ -4,7 +4,7 @@ views.argument_validator.none:
   type: sequence
   label: 'Basic validation'
   sequence:
-    - type: string
+    type: string
 
 views.argument_validator.php:
   type: mapping
@@ -25,8 +25,8 @@ views.argument_validator_entity:
       type: sequence
       label: 'Bundles'
       sequence:
-        - type: string
-          label: 'Bundle'
+        type: string
+        label: 'Bundle'
     access:
       type: boolean
       label: 'Access'
diff --git a/core/modules/views/config/schema/views.data_types.schema.yml b/core/modules/views/config/schema/views.data_types.schema.yml
index 50a075e..51ce002 100644
--- a/core/modules/views/config/schema/views.data_types.schema.yml
+++ b/core/modules/views/config/schema/views.data_types.schema.yml
@@ -17,7 +17,7 @@ views_display:
       type: sequence
       label: 'Fields'
       sequence:
-        - type: views.field.[plugin_id]
+        type: views.field.[plugin_id]
     pager:
       type: mapping
       label: 'Pager'
@@ -52,22 +52,22 @@ views_display:
       type: sequence
       label: 'No results behavior'
       sequence:
-        - type: views.area.[plugin_id]
+        type: views.area.[plugin_id]
     sorts:
       type: sequence
       label: 'Sorts'
       sequence:
-        - type: views.sort.[plugin_id]
+        type: views.sort.[plugin_id]
     arguments:
       type: sequence
       label: 'Arguments'
       sequence:
-        - type: views.argument.[plugin_id]
+        type: views.argument.[plugin_id]
     filters:
       type: sequence
       label: 'Filters'
       sequence:
-        - type: views.filter.[plugin_id]
+        type: views.filter.[plugin_id]
     filter_groups:
       type: mapping
       label: 'Groups'
@@ -79,8 +79,8 @@ views_display:
           type: sequence
           label: 'Groups'
           sequence:
-            - type: string
-              label: 'Operator'
+            type: string
+            label: 'Operator'
     style:
       type: mapping
       label: 'Format'
@@ -200,7 +200,7 @@ views_display:
       type: sequence
       label: 'Relationships'
       sequence:
-        - type: views.relationship.[plugin_id]
+        type: views.relationship.[plugin_id]
     css_class:
       type: string
       label: 'CSS class'
@@ -235,12 +235,12 @@ views_display:
       type: sequence
       label: 'Header'
       sequence:
-      - type: views.area.[plugin_id]
+        type: views.area.[plugin_id]
     footer:
       type: sequence
       label: 'Footer'
       sequence:
-      - type: views.area.[plugin_id]
+        type: views.area.[plugin_id]
     display_comment:
       type: label
       label: 'Display comment'
@@ -267,7 +267,7 @@ views_display:
       type: sequence
       label: 'Display extenders'
       sequence:
-       - type: views.display_extender.[%key]
+        type: views.display_extender.[%key]
 
 views_sort:
   type: views_handler
@@ -655,18 +655,18 @@ views_style:
       type: sequence
       label: 'Grouping field number %i'
       sequence:
-        - type: mapping
-          label: 'Field'
-          mapping:
-            field:
-              type: string
-              label: 'Field'
-            rendered:
-              type: boolean
-              label: 'Use rendered output to group rows'
-            rendered_strip:
-              type: boolean
-              label: 'Remove tags from rendered output'
+        type: mapping
+        label: 'Field'
+        mapping:
+          field:
+            type: string
+            label: 'Field'
+          rendered:
+            type: boolean
+            label: 'Use rendered output to group rows'
+          rendered_strip:
+            type: boolean
+            label: 'Remove tags from rendered output'
     row_class:
       type: string
       label: 'Row class'
@@ -727,8 +727,8 @@ views_filter:
           type: sequence
           label: 'User roles'
           sequence:
-            - type: string
-              label: 'Role'
+            type: string
+            label: 'Role'
     is_grouped:
       type: boolean
       label: 'Grouped filters'
@@ -764,14 +764,14 @@ views_filter:
           type: sequence
           label: 'Defaults'
           sequence:
-            - type: integer
-              label: 'Default'
+            type: integer
+            label: 'Default'
         group_items:
           type: sequence
           label: 'Group items'
           sequence:
-            - type: views.filter.group_item.[%parent.%parent.%parent.plugin_id]
-              label: 'Group item'
+            type: views.filter.group_item.[%parent.%parent.%parent.plugin_id]
+            label: 'Group item'
     plugin_id:
       type: string
       label: 'Plugin ID'
diff --git a/core/modules/views/config/schema/views.display.schema.yml b/core/modules/views/config/schema/views.display.schema.yml
index 2cb4673..d31678f 100644
--- a/core/modules/views/config/schema/views.display.schema.yml
+++ b/core/modules/views/config/schema/views.display.schema.yml
@@ -95,8 +95,8 @@ views.display.feed:
       type: sequence
       label: 'The feed icon will be available only to the selected displays.'
       sequence:
-        - type: string
-          label: 'Display'
+        type: string
+        label: 'Display'
 
 views.display.embed:
   type: views_display
@@ -110,8 +110,8 @@ views.display.attachment:
       type: sequence
       label: 'Attach to'
       sequence:
-        - type: string
-          label: 'Display'
+        type: string
+        label: 'Display'
     attachment_position:
       type: string
       label: 'Attachment position'
diff --git a/core/modules/views/config/schema/views.entity_reference.schema.yml b/core/modules/views/config/schema/views.entity_reference.schema.yml
index 3067041..1451368 100644
--- a/core/modules/views/config/schema/views.entity_reference.schema.yml
+++ b/core/modules/views/config/schema/views.entity_reference.schema.yml
@@ -18,5 +18,5 @@ entity_reference.views.handler_settings:
           type: sequence
           label: 'View arguments'
           sequence:
-            - type: string
-              label: 'Argument'
+            type: string
+            label: 'Argument'
diff --git a/core/modules/views/config/schema/views.field.schema.yml b/core/modules/views/config/schema/views.field.schema.yml
index de04690..b12c534 100644
--- a/core/modules/views/config/schema/views.field.schema.yml
+++ b/core/modules/views/config/schema/views.field.schema.yml
@@ -75,8 +75,8 @@ views.field.links:
       type: sequence
       label: 'Fields'
       sequence:
-        - type: string
-          label: 'Field'
+        type: string
+        label: 'Field'
     destination:
       type: boolean
       label: 'Include destination'
diff --git a/core/modules/views/config/schema/views.filter.schema.yml b/core/modules/views/config/schema/views.filter.schema.yml
index 969d212..44a5661 100644
--- a/core/modules/views/config/schema/views.filter.schema.yml
+++ b/core/modules/views/config/schema/views.filter.schema.yml
@@ -28,8 +28,8 @@ views.filter.combine:
       type: sequence
       label: 'Fields'
       sequence:
-        - type: string
-          label: 'Field'
+        type: string
+        label: 'Field'
 
 views.filter_value.date:
   type: views.filter_value.numeric
@@ -54,8 +54,8 @@ views.filter.in_operator:
       type: sequence
       label: 'Values'
       sequence:
-        - type: string
-          label: 'Value'
+        type: string
+        label: 'Value'
     expose:
       type: mapping
       label: 'Expose'
diff --git a/core/modules/views/config/schema/views.query.schema.yml b/core/modules/views/config/schema/views.query.schema.yml
index 8bab8d2..2f030fb 100644
--- a/core/modules/views/config/schema/views.query.schema.yml
+++ b/core/modules/views/config/schema/views.query.schema.yml
@@ -20,5 +20,5 @@ views.query.views_query:
       type: sequence
       label: 'Query Tags'
       sequence:
-        - type: string
-          label: 'Tag'
+        type: string
+        label: 'Tag'
diff --git a/core/modules/views/config/schema/views.row.schema.yml b/core/modules/views/config/schema/views.row.schema.yml
index fe61391..4378f0c 100644
--- a/core/modules/views/config/schema/views.row.schema.yml
+++ b/core/modules/views/config/schema/views.row.schema.yml
@@ -18,8 +18,8 @@ views.row.fields:
       type: sequence
       label: 'Inline'
       sequence:
-        - type: string
-          label: 'Inline'
+        type: string
+        label: 'Inline'
     separator:
       type: string
       label: 'Separator'
diff --git a/core/modules/views/config/schema/views.schema.yml b/core/modules/views/config/schema/views.schema.yml
index 6243b46..f7e089f 100644
--- a/core/modules/views/config/schema/views.schema.yml
+++ b/core/modules/views/config/schema/views.schema.yml
@@ -8,8 +8,8 @@ views.settings:
       type: sequence
       label: 'Display extenders'
       sequence:
-        - type: string
-          label: 'Display extender'
+        type: string
+        label: 'Display extender'
     skip_cache:
       type: boolean
       label: 'Disable views data caching'
@@ -62,8 +62,8 @@ views.settings:
       type: sequence
       label: 'Field rewrite elements'
       sequence:
-        - type: string
-          label: 'Element'
+        type: string
+        label: 'Element'
 
 views.view.*:
   type: config_entity
@@ -97,23 +97,23 @@ views.view.*:
       type: sequence
       label: 'Displays'
       sequence:
-        - type: mapping
-          label: 'Display settings'
-          mapping:
-            id:
-              type: string
-              label: 'Machine name'
-            display_title:
-              type: text
-              label: 'Title'
-            display_plugin:
-              type: string
-              label: 'Display plugin'
-            position:
-              type: integer
-              label: 'Position'
-            display_options:
-              type: views.display.[%parent.display_plugin]
+        type: mapping
+        label: 'Display settings'
+        mapping:
+          id:
+            type: string
+            label: 'Machine name'
+          display_title:
+            type: text
+            label: 'Title'
+          display_plugin:
+            type: string
+            label: 'Display plugin'
+          position:
+            type: integer
+            label: 'Position'
+          display_options:
+            type: views.display.[%parent.display_plugin]
 
 views_block:
   type: block_settings
diff --git a/core/modules/views/config/schema/views.style.schema.yml b/core/modules/views/config/schema/views.style.schema.yml
index 98a8ea7..f819aeb 100644
--- a/core/modules/views/config/schema/views.style.schema.yml
+++ b/core/modules/views/config/schema/views.style.schema.yml
@@ -56,8 +56,8 @@ views.style.table:
       type: sequence
       label: 'Columns'
       sequence:
-        - type: string
-          label: 'Columns name'
+        type: string
+        label: 'Columns name'
     default:
       type: string
       label: 'Default sort'
@@ -65,27 +65,27 @@ views.style.table:
       type: sequence
       label: 'Columns info'
       sequence:
-        - type: mapping
-          label:  'Column info'
-          mapping:
-            sortable:
-              type: boolean
-              label: 'Sortable'
-            default_sort_order:
-              type: string
-              label: 'Default order'
-            align:
-              type: string
-              label: 'Align'
-            separator:
-              type: string
-              label: 'Separator'
-            empty_column:
-              type: boolean
-              label: 'Hide empty columns'
-            responsive:
-              type: string
-              label: 'Responsive'
+        type: mapping
+        label:  'Column info'
+        mapping:
+          sortable:
+            type: boolean
+            label: 'Sortable'
+          default_sort_order:
+            type: string
+            label: 'Default order'
+          align:
+            type: string
+            label: 'Align'
+          separator:
+            type: string
+            label: 'Separator'
+          empty_column:
+            type: boolean
+            label: 'Hide empty columns'
+          responsive:
+            type: string
+            label: 'Responsive'
     override:
       type: boolean
       label: 'Override normal sorting if click sorting is used'
diff --git a/core/modules/views/tests/modules/views_test_data/config/schema/views_test_data.views.schema.yml b/core/modules/views/tests/modules/views_test_data/config/schema/views_test_data.views.schema.yml
index 59b5670..32722f8 100644
--- a/core/modules/views/tests/modules/views_test_data/config/schema/views_test_data.views.schema.yml
+++ b/core/modules/views/tests/modules/views_test_data/config/schema/views_test_data.views.schema.yml
@@ -18,8 +18,8 @@ views.style.mapping_test:
           type: sequence
           label: 'Numeric fields'
           sequence:
-            - type: string
-              label: 'Numeric field'
+            type: string
+            label: 'Numeric field'
         toggle_numeric_field:
           type: boolean
           label: 'Toggle numeric field'