game window size limit at 4k?

I have a dual-4k-projector setup (horizontal resolution of about 7000px) and I’m trying to preview my application with the game window.
However, it seems I cannot make the window larger than about 4000 pixels horizontally. Maximize button also leads to the window being “maximized” to that size. Is this some built-in limitation? Build and run the exe in fullscreen mode works, of course.

Unity 2022.2.0b6 on win10.

Unity has no such limitation built-in. How are you trying to make it bigger? Did you try doing it from code with “Screen.SetResolution(x, y, false)”?