That would probably need a change in MusicBee's code.
But, you can achieve it by using virtual tags.

Genre 1
$IsNull(<Genre>,,$If($Contains(<Genres>,;)="T",$Split(<Genres>,;,1),<Genre>))
Genre 2
$IsNull(<Genre>,,$If($Contains(<Genres>,;)="T",$Split(<Genres>,;,2),))
If you then select these new virtual tags to display (customize panel > configure fields > artwork fields) I believe it should work.
