So I'm running KSP 1.8 in windowed mode (1280x800) on my MacBook Pro / Catalina and the KSP window is very small, and UI elements are disproportionately large, except for the orbit lines in map mode, where the numbers (speed, altitude etc.) are very small.
Running a similar config in 1.73 (also windowed, but at 1280x720) does not exhibit the same behavior. This behavior was the same for KSP 1.6x, 1.5x and 1.4x as well. The primary difference being that the 1.73 install has some sort of global scaling factor applied to the entire window (not the individual elements such as UI_SCALE_XXX values), bringing the window size up to a reasonable size, while having all of the the UI elements sized reasonably well.
In the 1.73 instance, in the Settings|Graphics tab the Screen Resolution is set to "custom", while the settings.cfg file values are SCREEN_RESOLUTION_WIDTH = 1280 and SCREEN_RESOLUTION_HEIGHT = 720. The various UI_SCALE_XXX values are "1".
In the 1.8 instance, in the Settings|Graphics tab the Screen Resolution is set to 1280x800, while the settings.cfg file values are SCREEN_RESOLUTION_WIDTH = 1280 and SCREEN_RESOLUTION_HEIGHT = 800. The various UI_SCALE_XXX values are "1".
I'm guessing that it is something to do with the Unity upgrade, but don't know where to start looking for a fix. Is it possible to somehow add a scaling factor in KSP 1.8 to the entire window?