If you are not using a very large monitor you have to use Windows scaling. In Windows 10 the default scaling factor is 150% if you try to use 4K resolution. Even 150% may not be enough and as far as I can recall Fusion 360 does not use windows scaling very well or at all (kind of like Google Chrome using it's own scaling rather than Windows). On a 40 inch or bigger, if that fits on your desk, Fusion 360 is fine and very workable. Also don't try dual monitors if one is 4K and the other isn't, Windows 10 monitor scaling is broken in that scenario and you will have tons of problems when coming out of sleep mode.
@pbreed wrote:
Fusion is almost unusable on a 4K monitor.
Works fine at other resolutions...
I have a single 43" 4K monitor on my desk and Windows is set to 100% scaling rather than the default 150%. Everything in Fusion 360 appears as if it were on a 21-22" 1080 monitor with regard to icon size and text size, what is important for these non-Windows display scaling apps is that your DPI be kept in a reasonable range anything around 100-110 DPI will allow you to run Windows with no scaling and not suffer from tiny icons or tiny text.
To be honest, I do believe this is a Fusion issue and their code needs to allow for Windows to scale the display. All postions of the display including all icons and text.