Thanks for the help. I kind of learned the use of functions like list_union and so on, but still bad about using $, '(^|,)([^,]*? and similar
Will have to expand my knowledge. Maybe time will come when I can do all my custom columns without any help... It's not forbidden to dream
I changed it into program like this:
This should give me one nice list of tags and shelves for book detail window and for kindle collections.