Fix the white frameless windows
The new UI design of making the windows white and windows without frames is a poor design decision.
If you try to counteract the white-everwhere look, and select the 'dark' theme, then you have a black title bar on the windows, and then you can't see the 'minimize, restore & close' options.
If you've got multiple 'native' server 2019 applications open, its very difficult to differentiate where the edges of the windows are - so much I've had premier support staff get caught out by it when on remote support calls.
If you run 'older' products such as SCCM, and maybe open the service manager you'll get a window with a frame edge, you know the dimensions where that window is.
There needs to be some sort of middle ground here to fixing this.
Paul Deasy commented
Through process of elimination, it looks like the 'transparancy effects' being enabled causes the above frameless windows experience. Disable the setting, and you can go back to a way of seeing the edges of the windows!