@jennyd says
> should the "Overwrite existing mappings" option be "Update existing mappings"?
>   it currently sounds misleading when adding to existing tags, because it doesn't remove all the tags which >aren't being added to make the tag list consistent with what is entered. I agree that that's the most useful >behaviour, but the option name sounds as if it will do the other thing.

I think I probably agree with this. @fofr?