I've looked but no joy.

Title says it all but here more details just in case.

I always had my window taskbar buttons set up as follows:

left centre right
menu - shade title keep above - minimize - maximise - close

The default setup is without the keep above button which can still be accessed by right clicking on the taskbar but that is rather cumbersome.

Anybody know where this customization is hiding?

I can answer in a thrice

systemsettings .... -> workspace appearance -> window decorations -> configure buttons

Nice one

Many thanks, I was banging my head against the wall because of this but just couldn't find it.