I curse the MS developer/s who wrote the peep show listboxes: those non-resizable scrolling list boxes that display long lists in a peep hole that is just a few items long so you have to scroll endlessly to find what you need. This UI element has remained in the OS since I had hair on my head.
The OP indirectly explains why those listboxes were non-resizable:
“TM is one of the apps I'm most proud of because it is probably the first app to ever be fully resizable in all dimensions without any flicker.”
Win32 didn’t have an automatic layout engine. Resizing meant drawing your content while new mouse events were firing rapidly. It was hard enough to do flicker-free that Microsoft preferred fixed dialogs where possible.
(To be fair, it’s not like resizing is a solved problem even in 2020. For example on macOS, brand new apps ported from iOS using the Catalyst runtime seem to have absolutely terrible resize performance.)
