How to set Desktop Scaling to monitor(s) on macOS High Sierra+

Environment

macOS High Sierra+ / Mojave / BigSur

Issue

You would like to easily set Mac Retina display(s) to higher unsupported resolutions.

Resolution

Free - RDM
Shareware $14 - SwitchResX

Root Cause

macOS X only natively supports HiDPI modes on monitors with the most common Aspect Ratios.

More details - Guide: Fixing External Monitor Scaling and ‘Fuzziness’ Issues with MBP and OSX