In prior versions I could cycle any windows width between 3 stages of fixed width. This was the most useful feature for on-demand window placement. I have not yet found a way to recreate the behaviour and it is very important that it is the same hotkey that toggles the 3 steps cycling. I have no clue why this feature was removed but I have hunch that it has todo with Apples builtin window features. im using BST 1.9.12 on mac sequoia and it was a feature clickable. When you combine this feature with 4 square positioning, you have full control of any window with only two hotkeys, it was superb!
I'm currently not on my Mac, but you can scroll down in the keyboard shortcuts list, then you'll see the cycle options