diff --git a/app/assets/javascripts/discourse/app/controllers/user-private-messages.js b/app/assets/javascripts/discourse/app/controllers/user-private-messages.js
index 2ca079d6a6e..45c37747bd2 100644
--- a/app/assets/javascripts/discourse/app/controllers/user-private-messages.js
+++ b/app/assets/javascripts/discourse/app/controllers/user-private-messages.js
@@ -2,11 +2,27 @@ import Controller, { inject as controller } from "@ember/controller";
 import { action, computed } from "@ember/object";
 import { inject as service } from "@ember/service";
 import { alias, and, equal, readOnly } from "@ember/object/computed";
-import { tracked } from "@glimmer/tracking";
+import { cached, tracked } from "@glimmer/tracking";
 import I18n from "I18n";
 import DiscourseURL from "discourse/lib/url";
 
-export const PERSONAL_INBOX = "__personal_inbox__";
+const customUserNavMessagesDropdownRows = [];
+
+export function registerCustomUserNavMessagesDropdownRow(
+  routeName,
+  name,
+  icon
+) {
+  customUserNavMessagesDropdownRows.push({
+    routeName,
+    name,
+    icon,
+  });
+}
+
+export function resetCustomUserNavMessagesDropdownRows() {
+  customUserNavMessagesDropdownRows.length = 0;
+}
 
 export default class extends Controller {
   @service router;
@@ -25,19 +41,21 @@ export default class extends Controller {
   @readOnly("site.can_tag_pms") pmTaggingEnabled;
 
   get messagesDropdownValue() {
-    const parentRoute = this.router.currentRoute.parent;
+    let value;
 
-    if (Object.keys(parentRoute.params).length > 0) {
-      return this.router.urlFor(
-        parentRoute.name,
-        this.model.username,
-        parentRoute.params
-      );
-    } else {
-      return this.router.urlFor(parentRoute.name, this.model.username);
+    for (let i = this.messagesDropdownContent.length - 1; i >= 0; i--) {
+      const row = this.messagesDropdownContent[i];
+
+      if (this.router.currentURL.includes(row.id)) {
+        value = row.id;
+        break;
+      }
     }
+
+    return value;
   }
 
+  @cached
   get messagesDropdownContent() {
     const content = [
       {
@@ -66,6 +84,14 @@ export default class extends Controller {
       });
     }
 
+    customUserNavMessagesDropdownRows.forEach((row) => {
+      content.push({
+        id: this.router.urlFor(row.routeName, this.model.username),
+        name: row.name,
+        icon: row.icon,
+      });
+    });
+
     return content;
   }
 
diff --git a/app/assets/javascripts/discourse/app/lib/plugin-api.js b/app/assets/javascripts/discourse/app/lib/plugin-api.js
index b55155b5b87..91e666becb6 100644
--- a/app/assets/javascripts/discourse/app/lib/plugin-api.js
+++ b/app/assets/javascripts/discourse/app/lib/plugin-api.js
@@ -107,6 +107,7 @@ import DiscourseURL from "discourse/lib/url";
 import { registerNotificationTypeRenderer } from "discourse/lib/notification-types-manager";
 import { registerUserMenuTab } from "discourse/lib/user-menu/tab";
 import { registerModelTransformer } from "discourse/lib/model-transformers";
+import { registerCustomUserNavMessagesDropdownRow } from "discourse/controllers/user-private-messages";
 
 // If you add any methods to the API ensure you bump up the version number
 // based on Semantic Versioning 2.0.0. Please update the changelog at
@@ -2018,6 +2019,19 @@ class PluginApi {
   registerModelTransformer(modelName, transformer) {
     registerModelTransformer(modelName, transformer);
   }
+
+  /**
+   * EXPERIMENTAL. Do not use.
+   * Adds a row to the dropdown used on the `userPrivateMessages` route used to navigate between the different user
+   * messages pages.
+   *
+   * @param {string} routeName The Ember route name to transition to when the row is selected in the dropdown
+   * @param {string} name The text displayed to represent the row in the dropdown
+   * @param {string} [icon] The name of the icon that will be used when displaying the row in the dropdown
+   */
+  addUserMessagesNavigationDropdownRow(routeName, name, icon) {
+    registerCustomUserNavMessagesDropdownRow(routeName, name, icon);
+  }
 }
 
 // from http://stackoverflow.com/questions/6832596/how-to-compare-software-version-number-using-js-only-number
diff --git a/app/assets/javascripts/discourse/app/templates/user-private-messages-user.hbs b/app/assets/javascripts/discourse/app/templates/user-private-messages-user.hbs
index bc25f24dabb..125404af45f 100644
--- a/app/assets/javascripts/discourse/app/templates/user-private-messages-user.hbs
+++ b/app/assets/javascripts/discourse/app/templates/user-private-messages-user.hbs
@@ -39,8 +39,6 @@
       <span>{{i18n "user.messages.archive"}}</span>
     </LinkTo>
   </li>
-
-  <PluginOutlet @name="user-messages-nav" @connectorTagName="li" @args={{hash model=this.model}} />
 </UserNav::MessagesSecondaryNav>
 
 {{outlet}}
diff --git a/app/assets/javascripts/discourse/tests/acceptance/user-private-messages-test.js b/app/assets/javascripts/discourse/tests/acceptance/user-private-messages-test.js
index 8dc4313df4d..9ac356da93e 100644
--- a/app/assets/javascripts/discourse/tests/acceptance/user-private-messages-test.js
+++ b/app/assets/javascripts/discourse/tests/acceptance/user-private-messages-test.js
@@ -17,6 +17,8 @@ import {
   resetHighestReadCache,
   setHighestReadCache,
 } from "discourse/lib/topic-list-tracker";
+import { withPluginApi } from "discourse/lib/plugin-api";
+import { resetCustomUserNavMessagesDropdownRows } from "discourse/controllers/user-private-messages";
 
 acceptance(
   "User Private Messages - user with no group messages",
@@ -753,6 +755,30 @@ function testUserPrivateMessagesWithGroupMessages(needs, customUserProps) {
         "All tags is still selected in dropdown"
       );
     });
+
+    test("addUserMessagesNavigationDropdownRow plugin api", async function (assert) {
+      try {
+        withPluginApi("1.5.0", (api) => {
+          api.addUserMessagesNavigationDropdownRow(
+            "preferences",
+            "test nav",
+            "arrow-left"
+          );
+        });
+
+        await visit("/u/eviltrout/messages");
+
+        const messagesDropdown = selectKit(".user-nav-messages-dropdown");
+        await messagesDropdown.expand();
+
+        const row = messagesDropdown.rowByName("test nav");
+
+        assert.strictEqual(row.value(), "/u/eviltrout/preferences");
+        assert.ok(row.icon().classList.contains("d-icon-arrow-left"));
+      } finally {
+        resetCustomUserNavMessagesDropdownRows();
+      }
+    });
   }
 }