Hi Andreas,
I’ve (finally) found some time to try this 
but failed.
First issue is that I have no idea to which file I have to add this new class… for a test I’ve added it to my plugin configuration script in~/local/share/check_mk/web/plugins/wato/. But this doesn’t help, the result was that the check configuration disappeared 
So, what I now assume is that this list:
is somewhere statically defined and (currently) cannot be extended.
Anyone from the CheckMk team here who can confirm this? 