core/modules/outside_in/outside_in.api.php         | 23 +++++++---------------
 .../BlockPluginHasOffCanvasFormAccessCheck.php     | 16 ++++++++++++++-
 .../OutsideInBlockFormTest.php                     |  8 ++++----
 .../BlockPluginHasOffCanvasFormAccessCheckTest.php |  6 ++++--
 4 files changed, 30 insertions(+), 23 deletions(-)

diff --git a/core/modules/outside_in/outside_in.api.php b/core/modules/outside_in/outside_in.api.php
index c3ed73e..913036f 100644
--- a/core/modules/outside_in/outside_in.api.php
+++ b/core/modules/outside_in/outside_in.api.php
@@ -10,25 +10,16 @@
  * @{
  * Settings Tray API
  *
- * @section sec_overview Overview and terminology
- *
- * The goal of the Settings Tray module is to make administering blocks easier,
- * and therefore to make the site building experience faster and more pleasant.
- *
- * It achieves this by building on the infrastructure that the Contextual
- * Links module provides: Settings Tray provides a "Quick Edit" contextual link
- * for blocks. Clicking this contextual link opens the Settings Tray, which
- * allows to change the contents of the block (not the visibility conditions).
- * This means blocks can be modified without leaving the page.
- *
- * The Settings Tray uses a variant of a standard dialog: an off-canvas dialog.
- *
  * @section sec_api The API: the form in the Settings Tray
  *
  * By default, every block will show their built-in form in the Settings Tray.
- * However, many blocks would benefit from a tailored form which limits the form
- * to only the form items that affect the content of the rendered block: this
- * results in a better experience.
+ * However, many blocks would benefit from a tailored form which either:
+ * - limits the form to only the form items that affect the content of the
+ *   rendered block, or
+ * - adds additional form items to edit configuration that is rendered by the
+ *   block.
+ * This results in a better experience: the Settings Tray form always allows the
+ * user to change what is rendered by the block.
  *
  * Each block plugin can specify which form to use in the off-canvas dialog:
  * @code
diff --git a/core/modules/outside_in/src/Access/BlockPluginHasOffCanvasFormAccessCheck.php b/core/modules/outside_in/src/Access/BlockPluginHasOffCanvasFormAccessCheck.php
index e8536f7..83ebdef 100644
--- a/core/modules/outside_in/src/Access/BlockPluginHasOffCanvasFormAccessCheck.php
+++ b/core/modules/outside_in/src/Access/BlockPluginHasOffCanvasFormAccessCheck.php
@@ -4,6 +4,7 @@
 
 use Drupal\block\BlockInterface;
 use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Block\BlockPluginInterface;
 use Drupal\Core\Routing\Access\AccessInterface;
 
 /**
@@ -20,9 +21,22 @@ class BlockPluginHasOffCanvasFormAccessCheck implements AccessInterface {
    * @return \Drupal\Core\Access\AccessResultInterface
    *   The access result.
    */
-  public function access(BlockInterface $block) {
+  public function accessBlock(BlockInterface $block) {
     /** @var \Drupal\Core\Block\BlockPluginInterface $block_plugin */
     $block_plugin = $block->getPlugin();
+    return $this->accessBlockPlugin($block_plugin);
+  }
+
+  /**
+   * Checks access for accessing a block plugin's 'off_canvas' form.
+   *
+   * @param \Drupal\Core\Block\BlockPluginInterface $block_plugin
+   *   The block plugin whose 'off_canvas' form is being accessed.
+   *
+   * @return \Drupal\Core\Access\AccessResultInterface
+   *   The access result.
+   */
+  public function accessBlockPlugin(BlockPluginInterface $block_plugin) {
     return AccessResult::allowedIf($block_plugin->hasFormClass('off_canvas'));
   }
 
diff --git a/core/modules/outside_in/tests/src/FunctionalJavascript/OutsideInBlockFormTest.php b/core/modules/outside_in/tests/src/FunctionalJavascript/OutsideInBlockFormTest.php
index 4353355..191010d 100644
--- a/core/modules/outside_in/tests/src/FunctionalJavascript/OutsideInBlockFormTest.php
+++ b/core/modules/outside_in/tests/src/FunctionalJavascript/OutsideInBlockFormTest.php
@@ -186,8 +186,8 @@ public function providerTestBlocks() {
         'block_plugin' => 'outside_in_test_class',
         'new_page_text' => NULL,
         'element_selector' => 'span',
-        'label_selector' => 'h2',
-        'button_text' => 'Save Settings Tray test block: forms[off_canvas]=class',
+        'label_selector' => NULL,
+        'button_text' => NULL,
         'toolbar_item' => NULL,
       ],
       // This is the functional JS test coverage accompanying testPossibleAnnotations().
@@ -195,8 +195,8 @@ public function providerTestBlocks() {
         'block_plugin' => 'outside_in_test_none',
         'new_page_text' => NULL,
         'element_selector' => 'span',
-        'label_selector' => 'h2',
-        'button_text' => 'Save Settings Tray test block: forms[off_canvas] is not specified',
+        'label_selector' => NULL,
+        'button_text' => NULL,
         'toolbar_item' => NULL,
       ],
     ];
diff --git a/core/modules/outside_in/tests/src/Unit/Access/BlockPluginHasOffCanvasFormAccessCheckTest.php b/core/modules/outside_in/tests/src/Unit/Access/BlockPluginHasOffCanvasFormAccessCheckTest.php
index 0643688..104e45d 100644
--- a/core/modules/outside_in/tests/src/Unit/Access/BlockPluginHasOffCanvasFormAccessCheckTest.php
+++ b/core/modules/outside_in/tests/src/Unit/Access/BlockPluginHasOffCanvasFormAccessCheckTest.php
@@ -17,7 +17,8 @@
 class BlockPluginHasOffCanvasFormAccessCheckTest extends UnitTestCase {
 
   /**
-   * @covers ::access
+   * @covers ::accessBlock
+   * @covers ::accessBlockPlugin
    * @dataProvider providerTestAccess
    */
   public function testAccess(array $plugin_definition, AccessResultInterface $expected_access_result) {
@@ -26,7 +27,8 @@ public function testAccess(array $plugin_definition, AccessResultInterface $expe
     $block->getPlugin()->willReturn($block_plugin);
 
     $access_check = new BlockPluginHasOffCanvasFormAccessCheck();
-    $this->assertEquals($expected_access_result, $access_check->access($block->reveal()));
+    $this->assertEquals($expected_access_result, $access_check->accessBlock($block->reveal()));
+    $this->assertEquals($expected_access_result, $access_check->accessBlockPlugin($block_plugin));
   }
 
   public function providerTestAccess() {