Hello ChrisO, there is a build update for the 2020 version available here: https://www.pgmusic.com/support_macintoshupdates.htm#2020_426

In Band-in-a-Box when you enter a new time signature at the top (in blue lettering), a red line will appear on the bar to reflect that there is a change in the settings. But it will still show as 4/4 at the top. It will show a new time signature at the top if a new style with that time signature is loaded.

Best,
Chantelle