BiaB only recognizes 2/4, 3/4 or 4/4. You can change to a 6/8 via F5 at the measure you want but the chord sheet will not show 6/8. Notation will show the 6/8 notes but will not show a 6/8 time signature change. This assumes that you pick a 6/8 style in the F5 change. It is very confusing.

You might try this is Realband. I don't use Realband so I don't know if this is possible there.

I use MIDI and when I want to play something in other then 2/4, 3/4, or 4/4 I have to use other software.

Time signatures is one of my biggest BiaB complaints.

When you are at the checkout line and they ask if you found everything say "Why, are you hiding stuff?"

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware