RServer user options location

I am building a custom Docker image for RServer, and trying to figure out where user preferences are actually stored so I can preset some basic options like editor theme, fonts, etc.

I can start my container, and log into RServer, and then go to Tools->Global Options and change those options, and they persist even if I log out and back in, connect from another PC, etc, but I cannot for the life of me figure out where they are actually being stored. There is no .Rprofile being created in my home folder, and nothing in /etc/rstudio. Where else should I be looking?