Since I've been using MP3Tag I have been able to drag and drop both record and album to the cover art. Now I'm learning that you must use CTRL to do so for the second art. My Question is, should I bring other MP3s into 3.30, that have already been completed will the second cover not be touched or deleted? I have done over 3 thousand mp3s with dual covers and sometimes I may find a mistake and need to do some editing, and I would hate to lose all the time I have put into them.
If you want to add further covers with drag&drop, then always use the Ctrl key.
If you are not sure, use the context menu for the cover.
Simply viewing files does not modify the number of embedded pictures.