I recently updated BTT to 4.843. I used to be able to snap the Finder window to where I wanted it to be, then close it, and when I reopened that window, it would be in that same location. Now, when I close the window, it goes back to being a small window in the centre of the screen. I know there was some box I could check to get BTT to remember or default the window to the snapped location, but I can't find it now.
BTT can not do this, however usually macOS automatically remembers the sizes of windows when they are closed. Maybe there is something wrong with your Finder :-/
Every app saves its window sizes to its preferences file, for Finder that would be /Users/youruseraccount/Library/Preferences/com.apple.finder.plist
Maybe there is a permission issue and Finder is unable to write to its preferences. You can try deleting that plist, Finder will automtatically recreate it (but any Finder specific settings would be lost)
My initial thought was that it was Finder, and tried to sort it out with Apple Support. However, the issue does not persist when I shut down BTT. So something within BTT is causing the issue.
You mean, if you quit BTT your Finder windows will restore correctly to their previous size after you close them? And they don't if BTT is running?
That would be really weird as BTT doesn't do anything to Finder :-/
I just tried but my Finder windows seem to restore their size correctly regardless of whether BTT is running or not.
So for example, BTT is running. I take my Finder window and snap it to the right side of the screen. I close that window. I open the Finder window again and it is no longer snapped to the side. It is in the middle and small.
I close out of BTT and move the Finder window over to the right. I close out of that window. I open the Finder window again and it is exactly where I placed it before.
It's not so much an issue with Finder as it is an issue with snapping and BTT not keeping the set snap size of the window.