Yes you can Save the track as a Performance track then move it to the Audio track, enable Snap select the bars you don't like then right click Cut,
then open another instance of Biab and do the same with a track you just made an ending for or another song.SGU with frozen tracks, you enable Snap in the Audio Edit window, highlight the bars you like, right click Copy.
Then just paste that in the first instance.

Tutorial How to Bar to Bar Regeneration

Read through all of this also as there is a current bug when move the Audio track back to a Performance track.
https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=605464#Post605464

Create a backup SGU of all the frozen saved SGUs first.