Hello,

I'm playing with the KDE gestures and try to send Alt+F4. The gesture itself works for Alt+Left e.g., but it won't work for Alt+F4. How can I set a gesture that closed the current window?

Thanks!

Unusual - this should work fine. One reason I can think for it not working is due to Alt + F4 being a global shortcut, which is managed in a slightly different manner. Are you able to trigger other global shortcuts using gestures?

No.

Meta+E which is a user defined global shortcut does not work either. Alt+Left which no global shortcus does work.

Okay, it would appear that the gesture system does not support global shortcuts unfortunately - which includes Alt + F4 (which KWin handles in KDE).
If gestures are capable of executing arbitrary commands, then you could try the 'xte' command as noted here - viewtopic.php?f=67&t=111320&p=265917&hilit=xte#p265917