I have several menus or submenus that are only there to have sub-sub-menus under that heading. However you can still click on the submenu, for example, and it will bring up a blank page.
use teh wordpress menu (dashboard->appearances->menu) and in teh ‘Pages’ box, use the ‘Links’ tab. For teh URL use a pound sign(#) and for the ‘Link Text’ use what ever. You now have a menu item that does nothing and ou can use it for a spacer, submenu heading what ever.