Something else to consider, Ray. I've stopped worrying about importing Biab tracks because you can easily create them from scratch in RB. Once you've opened your Biab song, the chord grid is already there. Simply right click on any track below the Biab ones, select "midi" and pick an instrument, in this case drums and there's your new drum track. This thing about the missing midi drum track used to bug the crap out of me too until I learned to bypass it this way. You can change the style and create as many different midi drum tracks as you want. Changing the style only affects the one highlighted track. Same for all the instruments so that means your original Biab song that was created using one style for everything really becomes just a template for the chords. After that, you can right click one at a time 40 tracks if you want and create all different instrument tracks using all different styles using combinations of RT's and midi.
You want to get creative with your song? This is the real power of Real Band.

Bob

Biab/RB latest build, Win 11 Pro, Ryzen 5 5600 G, 512 Gig SSD, 16 Gigs Ram, Steinberg UR22 MkII, Roland Sonic Cell, Kurzweil PC3, Hammond SK1, Korg PA3XPro, Garritan JABB, Hypercanvas, Sampletank 3, more.