In Custom Menus you can redirect any of the standard menu commands and keyboard shortcuts to run a script of your own instead of its standard behaviour. This can be very useful—users are used to the presence of certain commands and menus and tend to use them, but you control the response they get.
I guess I wasn't clear.
The problem is NOT that I can't assign scripts/commands to menu choices, the problem is that FM (PC) automatically assigns EXIT to the left most menu item; and EXIT DOES NOT SHOW in the menu creation window. It looks like FM just adds it automatically and there is no way I can NOT have it show.