I'm an old-time fiddle player and I've tried various ways to import ABC files into BIAB. BIAB does not correctly import pickup notes and 1st and 2nd endings from ABC files. Because you're importing the Melody along with the chords, (and most likely some repeats) it is hard to edit the file once it's in BIAB. Here's the way that works best for me:

1. In EasyABC, prepare the ABC file. If there are any pickup notes, add the appropriate number of rests in front of the pickup notes...otherwise BIAB will put the pickup notes at the beginning of the measure, NOT at the end.

2. I prefer to manually unfold any repeats while still in EasyABC. In other words, if Part A repeats twice and the Part B repeats twice, remove all the repeats and copy and paste Part A and Part B in their respective places. You will now have an ABC file that has two Part A's and two Part B's. The transition between the parts (what used to be 1st and 2nd endings) will almost always require a little manual editing.

3. Many ABC files I've run across have mistakes in them...not enough beats in a measure, wrong chord changes, etc. Carefully inspect the file for these kinds of errors... and make sure there is a thin-thick bar at the end of the song.

4. Export the song as a MusicXML file.

5. In BIAB, Open>Open MusicXML file and choose the file.

6. In the next dialog box, uncheck "Load all XML tracks to Melody". This will keep your melody on a separate track so you can mute or unmute as you wish. When I'm learning a song, I unmute the melody track. But I can also mute it and use just the accompaniment.

Hope this helps some.