When I import a MIDI file to melody, I import just the one MIDI channel, and enter "1" in "# blank bars to insert at beginning" to offset the Lead-in measure. However, BIAB will only enter the MIDI melody starting in the Lead-in measure. No count-in measure, just melody, and then BIAB backing from measure 1. How do I prevent this?

Did you try putting "2" instead of "1"? By default, BIAB has a 2-bar count-in. It sounds like you might be starting the melody in the second bar of the count-in.

Regards,
Noel