Update monitoring docs with add panel button

This MR updates monitoring docs with the newly
added add panel button

doc/operations/metrics/dashboards/index.md

@@ -32,7 +32,7 @@ To create a new dashboard from the GitLab user interface:
 1. Sign in to GitLab as a user with Maintainer or Owner
    [permissions](../../../user/permissions.md#project-members-permissions).
 1. Navigate to your dashboard at **Operations > Metrics**.
-1. In the top-right corner of your dashboard, click the **{{ellipsis_v}}** **More actions** menu,
+1. In the top-right corner of your dashboard, click the **{ellipsis_v}** **More actions** menu,
    and select **Create new**:
    ![Monitoring Dashboard actions menu with create new item](img/actions_menu_create_new_dashboard_v13_3.png)
 1. In the modal window, click **Open Repository**, then follow the instructions
@@ -75,49 +75,26 @@ supported and won't be available in the UI.
 
 ## Add a new metrics panel to a dashboard
 
-> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/228761) in GitLab 13.3 behind a disabled [feature flag](../../../administration/feature_flags.md): `metrics_dashboard_new_panel_page`.
+> UI option [introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/228761) in GitLab 13.3.
 
 The metrics dashboard supports various [multiple panel types](../../../operations/metrics/dashboards/panel_types.md).
 You can quickly test how a panel configuration would display in your metrics dashboard
 with the **Add Panel** page:
 
 1. Sign in to GitLab as a user with Maintainer or Owner
-   [permissions](../../../user/permissions.md#project-members-permissions) on a
-   project that has the [feature flag enabled](#enable-or-disable-testing-metrics-panels).
-1. Open the URL `https://example.com/PROJECT/-/metrics/panel/new`, replacing
-   `example.com` with your domain name, and `PROJECT` with the name of your project,
-   to display the panel configuration page.
+   [permissions](../../../user/permissions.md#project-members-permissions).
+1. Click **Add panel** in the **{ellipsis_v}** **More actions** menu.
+
+   NOTE: **Note:**
+   You can add panel only to custom dashboards.
+
+   ![Monitoring Dashboard actions menu with add panel item](img/actions_menu_create_add_panel_v13_3.png)
 1. In the **Define and preview panel** section, paste in the YAML you want to
    preview in the **Panel YAML** field.
 1. Click **Preview panel**, and GitLab displays a preview of the chart below the
    `Define and preview panel` section:
    ![Monitoring Dashboard Add Panel page](img/metrics_dashboard_panel_preview_v13_3.png)
 
-### Enable or disable testing metrics panels
-
-Testing metrics panels in the UI is under development and not ready for production use. It's
-deployed behind a feature flag that's **disabled by default**.
-[GitLab administrators with access to the GitLab Rails console](../../../administration/feature_flags.md)
-can enable it for your instance. Testing metrics panels in the UI can be enabled or disabled per-project.
-
-To enable it:
-
-```ruby
-# Instance-wide
-Feature.enable(:metrics_dashboard_new_panel_page)
-# or by project
-Feature.enable(:metrics_dashboard_new_panel_page, Project.find(metrics_dashboard_new_panel_page))
-```
-
-To disable it:
-
-```ruby
-# Instance-wide
-Feature.disable(:metrics_dashboard_new_panel_page)
-# or by project
-Feature.disable(:metrics_dashboard_new_panel_page, Project.find(metrics_dashboard_new_panel_page))
-```
-
 ## Duplicate a GitLab-defined dashboard
 
 > - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/37238) in GitLab 12.7.
@@ -128,7 +105,7 @@ The resulting `.yml` file can be customized and adapted to your project.
 You can decide to save the dashboard `.yml` file in the project's **default** branch or in a
 new branch.
 
-1. Click **Duplicate current dashboard** in the **{{ellipsis_v}}** **More actions** menu.
+1. Click **Duplicate current dashboard** in the **{ellipsis_v}** **More actions** menu.
 
    NOTE: **Note:**
    You can duplicate only GitLab-defined dashboards.