I am not an expert, but did you use the script to install?
If you did, there you can find the “lightmassconfiguration.bat” where you can change quality settings
the only thing that does not ignore is: “Lightmass parameters and quality settings specified in the editor are ignored except for **Num Indirect Lighting Bounces” … **quoted from https://forums.unrealengine.com/deve…ss#post1460002