I imagine this is a common issue for Mac users: storage. My Mac fills up very quickly with system data, I will have an IT person looking into it soon but in the meantime I was wondering if there are hidden 3dm files stored anywhere that I could get rid of?
As you say, on Mac, macOS is responsible for creating and managing versions of files in all applications.
There is a test command that turns this off - but, of course, you won’t be able to get to earlier versions of a file and will be responsible yourself for making sure that the necessary backups are made. After running TestToggleMacAutosaveVersions, you will need to restart Rhino.
Apart from that, you can take a look in the trash can to see if there are any 3dm file you no longer need.
-wim