There should be a way to make edits to your menu while on content-only mode. The canvas edits should be restricted but the inspector menu should be reachable.

We should explore exposing the "menu list view" in the inspector of template parts or patterns that contain a menu when the user is on content-only mode.

There should be a clear way to reach that panel from the toolbar of the nav block and the template/pattern. Could be an "edit menu" that just toggles the inspector with the tab for the menu open.