PLEX and MP3TAG and multiple Genre

I am new to the notions of mp3 tags and PLEX. The further I investigate the more questions I have.

PLEX allows multiple genre designations. MP3TAG seems to only allow one.

Is there a way to set up the genre drop down in MP3TAG to allow multiple genre tags?

You can create several fields of the same type - try this with the extended tags dialogue first (Alt-T) where you click the "new" button and create a new GENRE field.
The see if that player of yours supports these multi-value fields.

Or select a file where you know that it already contains several genres and inspect it in the extended tags dialogue (Alt-T)