I hope that the function of finding duplicate files can be added. The basis of duplication is artist, song name, duration and file size, etc. Mp3tag is a amazing software for tag editor! Thanks!!
There are specialized tools that can already help you.
One of them is AllDup
You can fine tune your search for duplicates with multiple options:
Small addition: Link to the AllDup manual about "Find Similar Audio Files":
What will you do until if is implemented?
I found a number of almost 10 years old threads that deal with the problem of duplicates, e.g. here:
it has not yet been implemented.
And as tag data can be modified any which way you like it, it is not a good criterion to detect real duplicats. I assume that very often it is just the lack of information in the text in respect to the version (like, live, edit, remastered).
The length and size is also tricky as it most likely varies by a certain number of bytes - and how many of them would qualify to indicate a duplicate or a different version.
The only way out would be acoustic fingerprinting which would deal with the audio part - and that has not been within MP3tag's scope so far. MP3tag deals with the metadata, not the payload data.