Customising tags for my specific MP3 collection

[ohrenkino]

@Wolksby

Is it, then, possible to edit these fields in the same way as I was able to the Genres field, and which works a treat!

In short: Yes.
Except for _SEPARATOR all field definitions for the tag panel behave in the same way.

A look at the documentation would also have revealed the features:

Tag Panel – Mp3tag Documentation