When I attempt to set the Show Desktop hotkey inside of Mission Control to a mouse button it never seems to work. My preferred mouse button would be mouse button 4 (which is a little thumb button on the side of my mouse).
This used to work brilliantly but at some point it stopped. I believe this whole thing started with Leopard, so i've been seeing this behavior for quite some time.
I can set any other Mission Control shortcut to Mouse Button 4 and it works great. The Show Desktop shortcut does not work with any mouse button. The keyboard shortcuts work for everything though.
I'm not the only person to have seen this issue either. Here are some other people who experience my problem or a suspiciously similar problem.
http://forums.macrumors.com/showthread.php?t=1369627
'Show Desktop' Mission Control/Expose Not Functioning
Someone suggested removing the ~/Library/Preferences/com.apple.symbolichotkeys.plist
file which did not work for me.
I have a MacBook Pro (Retina, Mid 2012) and a Logitech G9 mouse. I would love some insight on how to fix this issue.