First of all, congratulations and thanks for a impresive program.
I'm trying to tag my huge collection of music (starting with many OST) and use mainly MusicBrainz.
I know Picard automatize this work, but need retain manual control of the actions, and mp3tag is perfect for that.
Ok, my suggestions....
In search result of music brainz windows :
Add column, for show language of album, this field exist in MusicBrainz.
Add column, for show icon if the selected result have cover image or not.
In the next window, when you select a result and need match the songs.
Green ink font, for the automatic match (same name and same duration (maybe choose a qty. of seconds of difference in options) , yellow ink if has a medium difference, and red for totally diferent name or duration.
This not is a sugestion, thanks for the posibility of order by time, it's very usefull.
I know, the spanish translation it's so good, but if you need help, say me
Of course you can edit your files with whatever information you like.
MusicBrainz will NOT tell you which songs are written in Italian, French, Spanish or whatever language.
As I quoted above, the "language" informations
There is actually no way using MusicBrainz to get the language of the lyrics itself, only in which language they are written on the cover.