I'm trying to do also some tuning with xkb
and I can figure out a workaround.
You can map a multimedia shortcut to the CapsLock
key <CAPS> { [ XF86ApplicationRight ] };
You have a pretty big list of supported shortcuts, just pick one..
Then you can map the CapsLock to perform switching application (ie. switching to next opened windows in one press without displaying an overlay)
It also works with regular cycling windows however it seems to only toggle the last windows.
I think that cycling windows needs a shortcut that have a modifier key in order to keep the list of opened windows (the thumbnails overlay) and then to allow cycling to the desired window.
But this is a workaround that actually works. In most distro the shortcut settings for this is under Windows Manager settings.