This is only a partial answer, because I've wondered the same thing!
If you go to the Library Browser, where you can select where to get problems from, like Open Problem Library, etc., one of the options is Set Definition Files. Then the dropdown menu for Browse From will have some predefined sets in there, but mostly from a Michigan gateway course. It does have set0 and setOrientation however. (And possibly any other exported sets from that particular course?)
For orientation sets in particular, I also have used the Open Problem Library, subject= WeBWorK, Chapter = WeBWorK Tutorial, and then several different sets appear.
So my question is: is there a way to access other predefined homework sets? We can tell from the problem path that a lot of the problems come from other school's homework sets, but I add problems individually to a homework set I'm making. When there are a lot of problems for a topic, it is cumbersome to go through enough of them, and sometimes, even if 2 problems come from different schools, they might actually have the same source, and I don't know this until after I've added both of them and see the note in the Homework Editor.
On a related note, I've been wondering about how to use the ModelCourses. I found my way to the Github page but I don't know what to do there. Can I download and import the set definition files from one or more of the ModelCourses?