Right-Hand Alt+Tab Keyboard Shortcut Problem

[2CV67]

With the arrival of Unity (mixed blessing...) I am reliving old times & using alt+tab again to switch between applications.

Actually, it is almost as convenient as having the application tabs visible, so I won't complain too much.

Small problem is that I use the mouse with my left hand & the keyboard mainly with my right.
Obviously, alt+tab is a left hand shortcut, so I keep dropping the mouse to alt+tab & vice-versa.

So I tried to add a right-hand shortcut to do the same thing.
It looks pretty simple: System Settings > Keyboard > Shortcuts > Custom Shortcuts > + > Name:"Switch" > Command:"Switch applications" > Apply > Click on "Switch" > Click on "Disabled" > Type "Ctrl" + "Menu".
But when I try to use Ctrl+Menu, I get an error message (see screenshot).

Whatever key combination I try as a custom shortcut gives the same type of error message.

I tried modifying the existing shortcut under "Navigation" and substituted Ctrl+Menu for Alt+Tab and that works perfectly.

But I really want to keep Alt+Tab as well as Ctrl+Menu.
So I tried to reintroduce a custom shortcut with Alt+Tab but that doesn't work either. (Screenshot is this attempt).



I suppose there is something wrong with the way I am trying to set up the custom shortcut, but can't see what that could be.

Thanks for any clues!