Thanks Charlie. I wasn't aware of BIAB's ability to record audio on multiple tracks.
I don't think it records multiple tracks, it just records the new track over top of the existing track.
They then become a single track, not multiple tracks.
To OP:
As previously mentioned Realband is made for this and comes with BiaB.
Try it.
Open your BiaB file in Realband and record 30 more tracks if you want, all separate.