> Well with QT_SCALE_FACTOR is goes and tells all the QT to behave in a particular way. It isn't a per application setting.
I understand that, but your window server is just another application. On Windows I wouldn't consider scale factor being an env var, and indeed it isn't set as such -- rather that value is set in the registry.
Maybe that's the answer -- Windows has a defacto method of setting system-wide env vars that every application inherits within a given personality but Linux/BSD does not.
I can live with that answer :-)