Saving different versions of your project

If what you were expecting/looking for was just something like a Save As… function on the File menu (like to make a kind of manual safety copy before making major changes), then the answer is just to i) close the project and then ii) in the Finder find and Duplicate the Project file and iii) rename it something sensible.

(Whether this is the best way to accomplish whatever your aim is is, of course, a separate matter.)