Being using MP3tag for a long time and love it but just came across a problem and not sure if an automated fix can be applied by greater minds than mine. I was tagging a multi set of classical music and noticed that on one of the cds there is a missing title description compared to the filename with the result that from then on all of the following titles are 'out' by one. So ideally Im looking for a way to move all of the titles from that point down by one and then I can insert the missing one against the filename - probably impossible?
Did you have a look at the numbering assistant?
In that function you can set a start value.
You may need to export the tag info for the current set of files you are working with, and add the missing line there. Then you can import them back with all of the files sorted in the correct order in mp3tag.
I don't believe you can automatically copy/paste from one file to another in a single pass within mp3tag, especially if one file is actually missing, or even if it is just the tags.