Tag field mapping

[ohrenkino]

Did you have a look at the documentation?

Mapping – Mp3tag Documentation

AFAI understand it: you map fields between different tag types that should be displayed as the same field in MP3tag.
If you want to copy a field contents to another field, see the FAQs:

Actions and batch-operations

How to copy one field value to another field? Example how to copy the content of the ARTIST field to the ALBUMARTIST field: Create a new action in an existing action group or make a new action group. Action type: Format value Field: ALBUMARTIST Format string: %artist% Note: If you want to copy all possible values of a field (in case you have multiple artist fields), the internal scripting function $meta_sep can be used in the format string, e.g., $meta_sep(artist,\\\\)