I think however, that if a problem set is open, and a student has completed a problem, then if I copy the problem's location to another set and delete the problem from the original set, the student's data for the problem would be lost.
I don't want to extend the deadline for the whole set, because I don't want to reward procrastinators for the sake of a couple problems that I didn't quite get to. But sometimes, I really like the problems! I'd like to just move them to the next open problem set so that anyone who did complete them still gets credit for them in the next set without having to redo them.
I've tried searching for help on this, but everything I find is about moving homework sets between courses, not about moving problems between homework sets in a course.
Does this ability exist?