OSX's windows features are poor at the best of times, so I use an app called Magnet which gives me the flexibility to line up windows side by side etc. To date, Magnet has worked with all my Mac programs with the exception of anything from Adobe and unfortunately it doesn't work with BIAB either. I presume that most software engineers never stopped for one second to consider whether their program would work with Magnet so there must be something about adopting standard settings for a program that makes Magnet work.

Magnet has featured in the Top 5 paid for apps on the mac app store for well over a year (and for all I know much longer than that). So, there's a lot of people out there with it and it clearly works with a lot of programs. It would be brilliant if BIAB for Mac could join that list.