Like they say, that depends on your needs.
If you need an extra file then I would duplicate ⌘+Shift+S my open file and name it whatever your convention is.
If I was doing it for me, instead of having umpteen files similar. I would just save a version point by hitting ⌘+S, this saves a point in the file I can go back to with Versions.
I like to keep my working files to one and my finished, cleaned up file and that is it - 2 files and any reference materials in a folder named for that project.
I am actualy clean up a persons rhino computer who just left and he had 6-7 versions of the file in his project folder, some titled 1.3dm, 2.3dm up to 6.3dm sometimes, and at least one untitled.3dm and then a finished file with the item name for a file name. That would drive me nuts, try searching for something using that convention.
If you start a new Rhino file, give it a name and save it somewhere. Then the first time you Duplicate either File menu or keyboard ⌘+SHIFT+S it is exactly like Save as. The untitled in file name shows it as a new duplicate /copy of the existing file.
If I Save as I get the same thing … albeit with the new Duplicated file name.
If you duplicate again, first you get to change the file name …
when you click in the filename you get the mini dropdown, where you also have the opportunity to move the file.
When you click on the Up-Down arrows to the right in the Move to box, the get the Recently accessed & Favourites Folders dropdown … are you still with me, we are going down the rabbit hole.
If that is not good enough, then you can click the other at the very bottom to access the full fledged Finder Window option.
usually for me the folders i am working in during a job are all in my recent places.
IHTH « Randy