Plasma have methods to show a grid of all desktops, all windows from all desktops, or all windows from current desktop.
Example: Normally Ctrl+F8 should show a grid of all desktops.
It *may* be confined to some systems running ati GPU.
It is visible with both
x11-driver-video-ati-7.10.0-1.1.mga6.src.rpm which fixed bug 22488
But may be because of other packages. mesa?
Not yet known when it broke, or what update broke it.
Problem got first logged at https://bugs.mageia.org/show_bug.cgi?id=22488#c21
And verified by me on another 64 bit, and a 32 bit system, all mga6.
As Plasma 5.12 is in the works - and hopefully soon shipped as update - i think it would be best to update the systems to that Plasma and related updates (from testing repo) and continue hunting this problem there - if it even exist there.
For those testers who have a system which show this problem, and accept it may brake ;)
Did a full update to Plasma5.12 etc in testing, by issuing
urpmi --auto-select --searchmedia testing
Still the same problem :(