Typically you attach a Menu to the Main Menubar not screens directly, and the screens then get attached to the menu you created. But could/should be possible to go to the screen directly.
I see from your screen shot you have Fixed Assets Commercial which has an example of how to create a new menu on the main menubar. It also has examples of how to add screens to menus. Look in the initMenu.js file in the assetmaint package and you will see script examples of creating a new main menu (the Maintenance menu) as well as attaching screens to menus.