I cannot find any documentation about it, or where to look the functions and console commands that affect AR. Besides the option to start the app in AR in the editor, I cannot see any function or console command like vr.bEnableStereo.
There is a way, in 4.19 though, to turn AR mode on and off with StartARSession(), either blueprints and c++ available.
Personally I wouldn’t stick to 4.18 since it’s missing a lot in terms of AR(XR) SDKs implemetation.