[kde-linux] Dumb question about Plasma

[Rosalind Mitchell]

I know this is a very silly question but...

Sometimes when I am manipulating the windows on my Plasma desktop I move the 
mouse cursor in a certain way and all the windows fragment into reduced-size 
windows all visible at once on the desktop.  

Unfortunately I've only been able to do this by accident.  Try as I might, I 
haven't been able to replicate the way I move the mouse to achieve this effect, 
though I've tried and tried.

Can somebody put me out of my misery, please, and tell me what it is I am 
doing accidentally that I can't seem to do deliberately?  

Rosie