Drop down window, pick one of your leagues. Import MFN-2 Rules (in entirety) to NBA Football League. One button push to add personal rules to a new league with a dispersal draft or any new league you join.
Adding rules now to a new league = hours of work = horrific.
I imagine it will be easier to do once the UI is updated. You can save a game plan and rules currently and load them in but it's definitely not a modern interface