thanks for your question.

The Menu button is "hard-wired" to showing and hiding the Remote 
Buddy menu. That's the only way to ensure a user can never get lost: 
all a user has to do is press the Menu button and the Remote Buddy 
menu appears - usually with a diagram showing the current mapping for 
orientation. From there, the user can go everywhere.

If the button for switching back to the Remote Buddy menu was freely 
configurable, a lot of the ease of use would be easily lost. You'd 
have to remember (or even worse: try out and possibly trigger 
unwanted actions) which button brings you back home into the main menu.

That's why the "Menu" entry internally exists (hard-wired to showing 
and hiding the RB menu) but is filtered out in the configuration 
dialogs.

Best regards, 
Felix