I meant that that one tag is in tags column. So I need to remove with some extra function. In ways I tried to remove it I always removes only the tag leaving a comma behind. So I get
, tag1, tag2
or
tag1, tag2,
or
,
instead of
tag1, tag2
I'll try your solution - works like a charm. Thank you.
It's nice to actually start to understand what a template does while just looking at it without calibre showing it to me

But I still need to learn a lot of functions...
Will try to transform other columns