diff --git a/core/lib/Drupal/Core/Block/Plugin/Block/PageTitleBlock.php b/core/lib/Drupal/Core/Block/Plugin/Block/PageTitleBlock.php
index 45899733e3..af1fb6ee37 100644
--- a/core/lib/Drupal/Core/Block/Plugin/Block/PageTitleBlock.php
+++ b/core/lib/Drupal/Core/Block/Plugin/Block/PageTitleBlock.php
@@ -11,6 +11,9 @@
  * @Block(
  *   id = "page_title_block",
  *   admin_label = @Translation("Page title"),
+ *   forms = {
+ *     "settings_tray" = FALSE,
+ *   },
  * )
  */
 class PageTitleBlock extends BlockBase implements TitleBlockPluginInterface {
diff --git a/core/modules/help/src/Plugin/Block/HelpBlock.php b/core/modules/help/src/Plugin/Block/HelpBlock.php
index 17dd88e95e..04f8bcbab6 100644
--- a/core/modules/help/src/Plugin/Block/HelpBlock.php
+++ b/core/modules/help/src/Plugin/Block/HelpBlock.php
@@ -15,7 +15,10 @@
  *
  * @Block(
  *   id = "help_block",
- *   admin_label = @Translation("Help")
+ *   admin_label = @Translation("Help"),
+ *   forms = {
+ *     "settings_tray" = FALSE,
+ *   },
  * )
  */
 class HelpBlock extends BlockBase implements ContainerFactoryPluginInterface {
diff --git a/core/modules/settings_tray/settings_tray.info.yml b/core/modules/settings_tray/settings_tray.info.yml
index bb2e36c4d9..c3adfd2d04 100644
--- a/core/modules/settings_tray/settings_tray.info.yml
+++ b/core/modules/settings_tray/settings_tray.info.yml
@@ -1,7 +1,7 @@
 name: 'Settings Tray'
 type: module
 description: 'Provides a sidebar to configure blocks on the page.'
-package: Core (Experimental)
+package: Core
 version: VERSION
 core: 8.x
 dependencies:
diff --git a/core/modules/settings_tray/settings_tray.module b/core/modules/settings_tray/settings_tray.module
index 208e1efc5d..114b4d9b2c 100644
--- a/core/modules/settings_tray/settings_tray.module
+++ b/core/modules/settings_tray/settings_tray.module
@@ -168,47 +168,10 @@ function settings_tray_toolbar_alter(&$items) {
  */
 function settings_tray_block_alter(&$definitions) {
   foreach ($definitions as &$definition) {
-    // If a block plugin already defines its own 'settings_tray' form, use that
-    // form instead of specifying one here.
-    if (isset($definition['forms']['settings_tray'])) {
-      continue;
-    }
-
-    switch ($definition['id']) {
-      // Use specialized forms for certain blocks that do not yet provide the
-      // form with their own annotation.
-      // @todo Move these into the corresponding block plugin annotations in
-      //   https://www.drupal.org/node/2896356.
-      case 'system_menu_block':
-        $definition['forms']['settings_tray'] = SystemMenuOffCanvasForm::class;
-        break;
-
-      case 'system_branding_block':
-        $definition['forms']['settings_tray'] = SystemBrandingOffCanvasForm::class;
-        break;
-
-      // No off-canvas form for the page title block, despite it having
-      // contextual links: it's too confusing that you're editing configuration,
-      // not content, so the title itself cannot actually be changed.
-      // @todo Move these into the corresponding block plugin annotations in
-      //   https://www.drupal.org/node/2896356.
-      case 'page_title_block':
-        $definition['forms']['settings_tray'] = FALSE;
-        break;
-
-      case 'system_main_block':
-        $definition['forms']['settings_tray'] = FALSE;
-        break;
-
-      case 'help_block':
-        $definition['forms']['settings_tray'] = FALSE;
-        break;
-
-      // Otherwise, use the block plugin's normal form rather than
-      // a custom form for Settings Tray.
-      default:
-        $definition['forms']['settings_tray'] = $definition['class'];
-        break;
+    // If a block plugin does not define its own 'settings_tray' form, use the
+    // plugin class itself.
+    if (!isset($definition['forms']['settings_tray'])) {
+      $definition['forms']['settings_tray'] = $definition['class'];
     }
   }
 }
diff --git a/core/modules/settings_tray/src/Form/SystemBrandingOffCanvasForm.php b/core/modules/system/src/Form/SystemBrandingOffCanvasForm.php
similarity index 96%
rename from core/modules/settings_tray/src/Form/SystemBrandingOffCanvasForm.php
rename to core/modules/system/src/Form/SystemBrandingOffCanvasForm.php
index 94c8052648..35e683080d 100644
--- a/core/modules/settings_tray/src/Form/SystemBrandingOffCanvasForm.php
+++ b/core/modules/system/src/Form/SystemBrandingOffCanvasForm.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\settings_tray\Form;
+namespace Drupal\system\Form;
 
 use Drupal\Core\Access\AccessResult;
 use Drupal\Core\Config\ConfigFactoryInterface;
@@ -10,9 +10,7 @@
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
- * The off-canvas form handler for the SystemBrandingBlock.
- *
- * @see settings_tray_block_alter()
+ * The settings_tray form handler for the SystemBrandingBlock.
  *
  * @internal
  */
diff --git a/core/modules/settings_tray/src/Form/SystemMenuOffCanvasForm.php b/core/modules/system/src/Form/SystemMenuOffCanvasForm.php
similarity index 97%
rename from core/modules/settings_tray/src/Form/SystemMenuOffCanvasForm.php
rename to core/modules/system/src/Form/SystemMenuOffCanvasForm.php
index 1f8114f498..82390bcbcc 100644
--- a/core/modules/settings_tray/src/Form/SystemMenuOffCanvasForm.php
+++ b/core/modules/system/src/Form/SystemMenuOffCanvasForm.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\settings_tray\Form;
+namespace Drupal\system\Form;
 
 use Drupal\Component\Plugin\PluginInspectionInterface;
 use Drupal\Core\Access\AccessResult;
@@ -18,9 +18,7 @@
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
- * The off-canvas form handler for the SystemMenuBlock.
- *
- * @see settings_tray_block_alter()
+ * The setting_tray form handler for the SystemMenuBlock.
  *
  * @internal
  */
diff --git a/core/modules/system/src/Plugin/Block/SystemBrandingBlock.php b/core/modules/system/src/Plugin/Block/SystemBrandingBlock.php
index 330528528d..fdb869a422 100644
--- a/core/modules/system/src/Plugin/Block/SystemBrandingBlock.php
+++ b/core/modules/system/src/Plugin/Block/SystemBrandingBlock.php
@@ -15,7 +15,10 @@
  *
  * @Block(
  *   id = "system_branding_block",
- *   admin_label = @Translation("Site branding")
+ *   admin_label = @Translation("Site branding"),
+ *   forms = {
+ *     "settings_tray" = "Drupal\system\Form\SystemBrandingOffCanvasForm",
+ *   },
  * )
  */
 class SystemBrandingBlock extends BlockBase implements ContainerFactoryPluginInterface {
diff --git a/core/modules/system/src/Plugin/Block/SystemMainBlock.php b/core/modules/system/src/Plugin/Block/SystemMainBlock.php
index beba38db4a..92f4430812 100644
--- a/core/modules/system/src/Plugin/Block/SystemMainBlock.php
+++ b/core/modules/system/src/Plugin/Block/SystemMainBlock.php
@@ -10,7 +10,10 @@
  *
  * @Block(
  *   id = "system_main_block",
- *   admin_label = @Translation("Main page content")
+ *   admin_label = @Translation("Main page content"),
+ *   forms = {
+ *     "settings_tray" = FALSE,
+ *   },
  * )
  */
 class SystemMainBlock extends BlockBase implements MainContentBlockPluginInterface {
diff --git a/core/modules/system/src/Plugin/Block/SystemMenuBlock.php b/core/modules/system/src/Plugin/Block/SystemMenuBlock.php
index 4489eb3015..a551ca64d3 100644
--- a/core/modules/system/src/Plugin/Block/SystemMenuBlock.php
+++ b/core/modules/system/src/Plugin/Block/SystemMenuBlock.php
@@ -16,7 +16,10 @@
  *   id = "system_menu_block",
  *   admin_label = @Translation("Menu"),
  *   category = @Translation("Menus"),
- *   deriver = "Drupal\system\Plugin\Derivative\SystemMenuBlock"
+ *   deriver = "Drupal\system\Plugin\Derivative\SystemMenuBlock",
+ *   forms = {
+ *     "settings_tray" = "\Drupal\system\Form\SystemMenuOffCanvasForm",
+ *   },
  * )
  */
 class SystemMenuBlock extends BlockBase implements ContainerFactoryPluginInterface {
diff --git a/core/modules/settings_tray/css/settings_tray.module.css b/core/themes/stable/css/settings_tray/settings_tray.module.css
similarity index 100%
copy from core/modules/settings_tray/css/settings_tray.module.css
copy to core/themes/stable/css/settings_tray/settings_tray.module.css
diff --git a/core/modules/settings_tray/css/settings_tray.motion.css b/core/themes/stable/css/settings_tray/settings_tray.motion.css
similarity index 100%
copy from core/modules/settings_tray/css/settings_tray.motion.css
copy to core/themes/stable/css/settings_tray/settings_tray.motion.css
diff --git a/core/modules/settings_tray/css/settings_tray.theme.css b/core/themes/stable/css/settings_tray/settings_tray.theme.css
similarity index 100%
copy from core/modules/settings_tray/css/settings_tray.theme.css
copy to core/themes/stable/css/settings_tray/settings_tray.theme.css
diff --git a/core/modules/settings_tray/css/settings_tray.toolbar.css b/core/themes/stable/css/settings_tray/settings_tray.toolbar.css
similarity index 100%
copy from core/modules/settings_tray/css/settings_tray.toolbar.css
copy to core/themes/stable/css/settings_tray/settings_tray.toolbar.css
diff --git a/core/themes/stable/stable.info.yml b/core/themes/stable/stable.info.yml
index 3f019d065b..04110695ba 100644
--- a/core/themes/stable/stable.info.yml
+++ b/core/themes/stable/stable.info.yml
@@ -169,6 +169,15 @@ libraries-override:
         css/quickedit.theme.css: css/quickedit/quickedit.theme.css
         css/quickedit.icons.theme.css: css/quickedit/quickedit.icons.theme.css
 
+  settings_tray/drupal.settings_tray:
+    css:
+      component:
+        css/settings_tray.module.css: css/settings_tray/settings_tray.module.css
+        css/settings_tray.motion.css: css/settings_tray/settings_tray.motion.css
+        css/settings_tray.toolbar.css: css/settings_tray/settings_tray.toolbar.css
+      theme:
+        css/settings_tray.theme.css: css/settings_tray/settings_tray.theme.css
+
   shortcut/drupal.shortcut:
     css:
       theme: