JE, if you have the Windows version of BiaB, then you also have RealBand. I think this is the best and easiest option for you to undertake your task.

You can lay the 3 MIDI files out on three separate tracks, then cut and paste as required. RealBand is a DAW, and has the tools to undertake this. You can also output to a file that can then open/run in BiaB


BIAB & RB2026 Win.(Audiophile), Windows 10 Pro & Windows 11, Cakewalk Bandlab, Izotope Prod.Bundle, Roland RD-1000, Synthogy Ivory, Session Keys Grand S & Electric R, Kontakt, Focusrite 18i20, KetronSD2, NS40M, Pioneer Active Monitors.