You can assign the F2 key, but it does not work.
Yes, indeed, I see this too, but there is nothing in the code that could explain that...
The problem is not specific to xfwm4, but also shows in the keyboard shortcut editor. I guess this could be related to gtk+.
In my case, the keyboard shortcut works.
Moreover after some steps, I managed to work again the manager shortcut !!!
I assign F2 to the keyboard shortcut.
I delete the previous shortcut.
I re-assign the shortcut in the windows manager.
The problem appear when you use a shortcut (ALT or CTRL) 'X' in the windows manager and 'X' in the keyboard shortcut (and also in the other order).
The shortcut ,that works, seems to depend on the order of assignement between the wm and the keyboard.
I have this problem too. It seems that an application's keybindings take precedence over the wm's. F1 and F2 have problems for me while F3 and F4 work fine. This used to work fine in 4.2 however. Was there code that might have been removed in 4.4 which gave precedence to the WM?
I have the same bug on xubuntu hardy.
This bug affect the 2 keys F1 and F2.
This seems not to be bounded to any application precedence, because I can reconfigure using xmodmap F1 and F2 Keys to F21 and F22 (no application bind those keys)
Works fine here now with the latest master branches of libxfce4ui and xfwm4, please reopen if you can still reproduce with that code.