unexpected "show desktop" shortcut (KDE4)

[René J.V. Bertin]

Hi,

I hit an accidental and as yet unidentified shortcut and am now seeing a "Show Desktop" entry in the task switcher. I'm 95% sure I deactivated the "Show Desktop Icon" option in the task switcher settings. Is there a shortcut to activate this option? 

To give an idea what keys I may have hit: I triggered this by a borked attempt to use the hardware shortcut Fn-F2 (turns off backlighting); the Fn key sits between the Ctrl and "Windows" keys. 

Thanks,
René