diff --git a/core/modules/toolbar/config/install/toolbar.settings.yml b/core/modules/toolbar/config/install/toolbar.settings.yml
new file mode 100644
index 0000000..7b920b3
--- /dev/null
+++ b/core/modules/toolbar/config/install/toolbar.settings.yml
@@ -0,0 +1,2 @@
+admin_tray:
+  menu_name: 'admin'
diff --git a/core/modules/toolbar/config/schema/toolbar.schema.yml b/core/modules/toolbar/config/schema/toolbar.schema.yml
new file mode 100644
index 0000000..84830ae
--- /dev/null
+++ b/core/modules/toolbar/config/schema/toolbar.schema.yml
@@ -0,0 +1,13 @@
+# Schema for the configuration files of the Toolbar module.
+
+toolbar.settings:
+  type: config_object
+  label: 'Toolbar settings'
+  mapping:
+    admin_tray:
+      type: mapping
+      label: 'Admin tray settings'
+      mapping:
+        menu_name:
+          type: string
+          label: 'Menu to use in the toolbar admin tray'
diff --git a/core/modules/toolbar/src/Controller/ToolbarController.php b/core/modules/toolbar/src/Controller/ToolbarController.php
index c94e35b..382fd7c 100644
--- a/core/modules/toolbar/src/Controller/ToolbarController.php
+++ b/core/modules/toolbar/src/Controller/ToolbarController.php
@@ -70,16 +70,8 @@ public static function preRenderAdministrationTray(array $element) {
     // Load the administrative menu. The first level is the "Administration"
     // link. In order to load the children of that link, start and end on the
     // second level.
-    $parameters = new MenuTreeParameters();
-    $parameters->setMinDepth(2)->setMaxDepth(2)->onlyEnabledLinks();
-    // @todo Make the menu configurable in https://www.drupal.org/node/1869638.
-    $tree = $menu_tree->load('admin', $parameters);
-    $manipulators = [
-      ['callable' => 'menu.default_tree_manipulators:checkAccess'],
-      ['callable' => 'menu.default_tree_manipulators:generateIndexAndSort'],
-      ['callable' => 'toolbar_menu_navigation_links'],
-    ];
-    $tree = $menu_tree->transform($tree, $manipulators);
+    /** @var \Drupal\Core\Menu\MenuLinkTreeElement[] $tree */
+    $tree = static::getAdminTrayMenuTree(2, 2);
     $element['administration_menu'] = $menu_tree->build($tree);
     return $element;
   }
@@ -94,16 +86,8 @@ public static function preRenderGetRenderedSubtrees(array $data) {
     // Load the administration menu. The first level is the "Administration"
     // link. In order to load the children of that link and the subsequent two
     // levels, start at the second level and end at the fourth.
-    $parameters = new MenuTreeParameters();
-    $parameters->setMinDepth(2)->setMaxDepth(4)->onlyEnabledLinks();
-    // @todo Make the menu configurable in https://www.drupal.org/node/1869638.
-    $tree = $menu_tree->load('admin', $parameters);
-    $manipulators = [
-      ['callable' => 'menu.default_tree_manipulators:checkAccess'],
-      ['callable' => 'menu.default_tree_manipulators:generateIndexAndSort'],
-      ['callable' => 'toolbar_menu_navigation_links'],
-    ];
-    $tree = $menu_tree->transform($tree, $manipulators);
+    /** @var \Drupal\Core\Menu\MenuLinkTreeElement[] $tree */
+    $tree = static::getAdminTrayMenuTree(2, 4);
     $subtrees = [];
     // Calculated the combined cacheability of all subtrees.
     $cacheability = new CacheableMetadata();
@@ -140,4 +124,47 @@ public static function trustedCallbacks() {
     return ['preRenderAdministrationTray', 'preRenderGetRenderedSubtrees'];
   }
 
+  /**
+   * Returns the name of the menu to use for the 'Manage' tray in the toolbar.
+   *
+   * This is here as a separate method to make it easy for contributed and
+   * custom modules to extend this controller and change the behavior without
+   * having to duplicate a lot of other code.
+   *
+   * @return string
+   *   The machine name of the menu to use for the 'Manage' tray.
+   *
+   * @internal
+   */
+  public static function getAdminTrayMenuName() : string {
+    return \Drupal::config('toolbar.settings')->get('admin_tray.menu_name');
+  }
+
+  /**
+   * Returns the menu tree to use for the 'Manage' tray in the toolbar.
+   *
+   * @param int $min_depth
+   *   The minimum depth of menu items to load and use.
+   * @param int $max_depth
+   *   The maximum depth of menu items to load and use.
+   *
+   * @return \Drupal\Core\Menu\MenuLinkTreeElement[]
+   *   The loaded and processed menu tree to use for the 'Manage' tray.
+   *
+   * @internal
+   */
+  public static function getAdminTrayMenuTree($min_depth, $max_depth) : array {
+    $menu_tree = \Drupal::service('toolbar.menu_tree');
+    $parameters = new MenuTreeParameters();
+    $parameters->setMinDepth($min_depth)->setMaxDepth($max_depth)->onlyEnabledLinks();
+    $admin_tray_menu = static::getAdminTrayMenuName();
+    $tree = $menu_tree->load($admin_tray_menu, $parameters);
+    $manipulators = [
+      ['callable' => 'menu.default_tree_manipulators:checkAccess'],
+      ['callable' => 'menu.default_tree_manipulators:generateIndexAndSort'],
+      ['callable' => 'toolbar_menu_navigation_links'],
+    ];
+    return $menu_tree->transform($tree, $manipulators);
+  }
+
 }
diff --git a/core/modules/toolbar/tests/modules/toolbar_custom_admin_tray_menu/config/install/system.menu.custom.yml b/core/modules/toolbar/tests/modules/toolbar_custom_admin_tray_menu/config/install/system.menu.custom.yml
new file mode 100644
index 0000000..d0ff9cd
--- /dev/null
+++ b/core/modules/toolbar/tests/modules/toolbar_custom_admin_tray_menu/config/install/system.menu.custom.yml
@@ -0,0 +1,6 @@
+langcode: en
+status: true
+dependencies: {  }
+id: custom
+label: Custom
+description: ''
diff --git a/core/modules/toolbar/tests/modules/toolbar_custom_admin_tray_menu/toolbar_custom_admin_tray_menu.info.yml b/core/modules/toolbar/tests/modules/toolbar_custom_admin_tray_menu/toolbar_custom_admin_tray_menu.info.yml
new file mode 100644
index 0000000..1664ade
--- /dev/null
+++ b/core/modules/toolbar/tests/modules/toolbar_custom_admin_tray_menu/toolbar_custom_admin_tray_menu.info.yml
@@ -0,0 +1,7 @@
+name: 'Custom toolbar admin tray menu'
+type: module
+description: 'Support module for testing toolbar with a custom admin tray menu.'
+package: Testing
+version: VERSION
+dependencies:
+  - drupal:toolbar
diff --git a/core/modules/toolbar/tests/modules/toolbar_custom_admin_tray_menu/toolbar_custom_admin_tray_menu.links.menu.yml b/core/modules/toolbar/tests/modules/toolbar_custom_admin_tray_menu/toolbar_custom_admin_tray_menu.links.menu.yml
new file mode 100644
index 0000000..f852e69
--- /dev/null
+++ b/core/modules/toolbar/tests/modules/toolbar_custom_admin_tray_menu/toolbar_custom_admin_tray_menu.links.menu.yml
@@ -0,0 +1,8 @@
+custom.base:
+  title: Custom menu base link
+  menu_name: custom
+  route_name: '<nolink>'
+custom.link:
+  title: Custom menu link
+  parent: custom.base
+  route_name: '<front>'
diff --git a/core/modules/toolbar/tests/src/Functional/ToolbarCustomAdminTrayMenuTest.php b/core/modules/toolbar/tests/src/Functional/ToolbarCustomAdminTrayMenuTest.php
new file mode 100644
index 0000000..cf19c49
--- /dev/null
+++ b/core/modules/toolbar/tests/src/Functional/ToolbarCustomAdminTrayMenuTest.php
@@ -0,0 +1,71 @@
+<?php
+
+namespace Drupal\Tests\toolbar\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Tests overriding the toolbar's admin tray menu.
+ *
+ * @group toolbar
+ */
+class ToolbarCustomAdminTrayMenuTest extends BrowserTestBase {
+
+  /**
+   * A user with permission to access the toolbar.
+   *
+   * @var \Drupal\user\UserInterface
+   */
+  protected $adminUser;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'toolbar',
+    'toolbar_custom_admin_tray_menu',
+    'test_page_test',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    // Set admin_tray.menu_name settings to 'custom' menu.
+    $config = $this->container->get('config.factory')->getEditable('toolbar.settings');
+    $config->set('admin_tray.menu_name', 'custom');
+    $config->save();
+
+    // Create an administrative user and log it in.
+    $this->adminUser = $this->drupalCreateUser([
+      'access toolbar',
+      'access administration pages',
+    ]);
+    $this->drupalLogin($this->adminUser);
+  }
+
+  /**
+   * Tests the custom admin tray menu.
+   */
+  public function testToolbarCustomAdminTrayMenu() {
+    $this->drupalGet('test-page');
+    $this->assertSession()->statusCodeEquals(200);
+
+    // Assert that the toolbar is present in the HTML.
+    $this->assertRaw('id="toolbar-administration"');
+
+    // Assert that the "Content" link is not present.
+    $this->assertNoRaw('href="/admin/content"');
+
+    // Assert that the custom link is present.
+    $this->assertRaw('Custom menu link');
+  }
+
+}
diff --git a/core/modules/toolbar/tests/src/Functional/ToolbarSettingsUpdateTest.php b/core/modules/toolbar/tests/src/Functional/ToolbarSettingsUpdateTest.php
new file mode 100644
index 0000000..fe45eda
--- /dev/null
+++ b/core/modules/toolbar/tests/src/Functional/ToolbarSettingsUpdateTest.php
@@ -0,0 +1,42 @@
+<?php
+
+namespace Drupal\Tests\toolbar\Functional;
+
+use Drupal\FunctionalTests\Update\UpdatePathTestBase;
+
+/**
+ * Tests updating toolbar module's configuration.
+ *
+ * @group toolbar
+ */
+class ToolbarSettingsUpdateTest extends UpdatePathTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setDatabaseDumpFiles() {
+    $this->databaseDumpFiles = [
+      __DIR__ . '/../../../../system/tests/fixtures/update/drupal-8.8.0.bare.standard.php.gz',
+    ];
+  }
+
+  /**
+   * Ensures that update hook is run for "toolbar" module.
+   */
+  public function testUpdateToolbarSettings() {
+    $config = $this->config('toolbar.settings');
+    $this->assertNull($config->get('admin_tray.menu_name'));
+
+    // Run updates.
+    $this->runUpdates();
+
+    $config = $this->config('toolbar.settings');
+    $this->assertNotNull($config->get('admin_tray.menu_name'));
+  }
+
+}
diff --git a/core/modules/toolbar/toolbar.install b/core/modules/toolbar/toolbar.install
new file mode 100644
index 0000000..04ace29
--- /dev/null
+++ b/core/modules/toolbar/toolbar.install
@@ -0,0 +1,16 @@
+<?php
+
+/**
+ * @file
+ * Install, update and uninstall functions for the toolbar module.
+ */
+
+/**
+ * Sets a default value for the admin_tray.menu_name setting.
+ */
+function toolbar_update_9201() {
+  \Drupal::service('config.factory')
+    ->getEditable('toolbar.settings')
+    ->set('admin_tray.menu_name', 'admin')
+    ->save();
+}