Hi, i know this is not really the right place since this is not really about Krita but i thought if there is an answer, one of this crowd would know it:
The most useful keys on my keyboard for using Krita are shift and ctrl. So i tried using the kde config dialog to set two buttons on my wacom intuos pro medium to those.
Since i also use undo and redo a lot i set another two buttons to ctrl-z and ctrl-shift-z.
My problem is: the first set of buttons do nothing and the second just both create a "z".
I'm under arch linux and using kde-wacomtablet-git from aur. kcm-wacomtablet gave the same result.
Can anybody here help me?

[Edit]
I tried xsetwacom but it seems to suffer from the same problem.
Maybe the kde uses it internally?
I filed a bug at linuxwacom and hope for the best: https://sourceforge.net/p/linuxwacom/bugs/269/
[/Edit]

Sorry for replying to my own post. I just wanted to tell the people who have read it the outcome.
My problem was really a bug in xsetwacom and was triggered by me having german and us-dvorak keymap in the kde keymap switcher.
There is now a patch attached to the bug i opened and since the developer i talked to was very helpful and very quick i expect it will be in the git repository soon and in the next release.
I am very thankful that this was resolved so quickly.
Just wanted to tell you the outcome so anyone experiencing similar problems can go for the patch as long as it's not released.
Sorry again for posting slightly OT here.

Ok, thanks for getting back with more information!