Thanks for the video. I'm attempting to create a drawer handle that has a arc on the inside and a spline on the outside. This helped, but didn't completely teach how I might achieve this element for my cabinets and drawers.
Splines can be a bit tricky and may cause some issues but I would have to see what you are wanting to model to know what might be the best way. Sorry this was not completely helpful for you.
That could be a sweep. You might first make a profile with that then load that into another family where you use it as a sweep. The profile can have those inward angles.
