I doubt its possible without base operating system or display card integration, but will we ever see window or split region scaling?

A couple of decades ago, the company I worked for had an SGI Indy workstation and the window manager had a scaling feature where a window could be scaled up or down without changing its size.

Some third party RDP applications will do this now, allowing you to change an RDP session window's size without changing the remote desktop session size. IE, you open a 1280x1024 window to a remote system and shrink the local window by 25% and the RDP session remains at 1280x1024 but the local display version merely scales down. It's an inbuilt feature of the MS RDP client and can be done manually by editing an RDP session file to change the remote desktop size vs. the display size.

I've used it occasionally when working on a project where I needed more desktops at a local monitor full screen native resolution than I had display space, but only needed to work intensively on one at a time. I'd put 4 scaled RDP sessions on one monitor at my local full screen resolution and be reasonably able to track status in them while I worked on another monitor at 1:1 scale/resolution.

This would be pretty cool to do for *any* window on demand -- shrink the window's display footprint while scaling the content, and extremely useful on say a very high res single monitor setup that was normally display scaled, since the scaled-down version would retain its detail.

Large 4k displays usable at native resolution kind of make this somewhat redundant, but I still think it would be useful. Even with a 4k display at 1:1, today's application windows are so piggish with layouts that you lose a lot of useful display space.