It’s been a process making a bow. I’ve tried out more techniques than I thought I had to. You should try to think of these things in Marvelous designer in terms of real world sewing, though when I’m tweaking my look for aesthetics that eventually goes out the window. So I’m trying to make the bow from this costume:

It’s a large bow, nearly three times the diameter of the waist, with ribbon ends that come out at a static curvature.

After trying a few things, my current way to make a bow is to basically create a tube, the open ends of which sew together and that a rectangle scrunching it in the middle. It is also helpful to pin the bow fabric to itself in the middle to form the bow crease. If you don’t do this the bow is free to bend concave or convex and it can be annoying when trying to actively edit the pattern.