@buddhaauthor & @Morgan_Hardwood, Sorry the late answer.
Yes, RT will have all user data in the location ~/Library/Application Support/RawTherapee from now on. And yes, ~/Library/Application Support/ is the right location for all Mac application user data. It’s normally hidden just like on Windows (AppData) and Linux (“dot” folders).
It will be in the manual once we’ve ironed out all the issues with the Mac builds.
Thanks for your patience.
Partha