It would be nice to have an option to keep existing tags when pasting.
Say, I have an old_file.mp3 with Title and Artist. And a new_file.mp3 with RG tags.
Currently, if I copy tags from old_file and paste them into new_file, the RG tags will be lost.
It would be useful if there was an option to keep in the target file all the tags that are not present (or present but empty) in the source file.