In Gothru Overlay editor you are able to create a multilevel menu via Overlay Menu Settings (Plugin Manager > Menu > Side Menu) as well as via the Active Plugin (Active Plugins > Side Menu).
In addition to articles about Menu Overlay, this article will be looking at the steps to create a submenu.
How to add a Sub-menu?
1. Under the Menu settings, navigate to the Menu list.
2. On the Menu list, add standard Menu lists using the Add text, Link, Hotspot or Active Pano.
3. Select the menu list that you want to use as a submenu and drag them below the target menu.
In this example, we will add Business class bar, Business class seat, and Business class bed to the target menu, SAS Business Class.
4. Click on the "in" button on the intended sub-menu. You will see that it's automatically added to the target menu or parent menu.
5. If you want to exclude the sub-menu from the parent menu, you can click the “out” button on the selected sub-menu.
6. Click "Save" and “Publish” to see the results.