Thanks, that's a nice idea! I did use a workaround with adding a tag "added" (in my case: "needs edition"

) but didn't know it is possible to add such a tag automatically. Where can I choose this option?
I am not sure if I will clear all tags in bulk, though. Sometimes they contain useful information (mostly ISBN so don't need to look for it in the book then). It would be nice if Calibre new when an ISBN is given as a tag.