This might seem like a bit of a strange one, since the UI is clear and readable in 4k (usually the reason somebody wants scaling) in ACEO, there are no worries there, but its something I would love to see still.
I play in 4k, but I personally find the tooltips and popup windows to be ‘too large’, covering so much of the display area. I would love a way to make them something like 25% to 50% smaller.
Also, with those windows, it would be neat if they could be pinned and dragged around, to be left open, i.e the one when clicking on a stand, although only if it could be scaled down.
Edit: After posting, I just took a quick look to refresh my memory… not played since last night
I wouldn’t actually mind reducing the whole UI… I guess I am used to things being smaller ( I run Windows without scaling (so 100%) in 4k, on a 32" screen.