This is an age-old topic; some of the best answers are from 2012; however, after some hours spent search and implementing/trying solutions I found on the forum discussion, I’m compelled to believe:
There must be a better way!
The best solution I have found is simple; offset curves in both directions; loft and look for the union of regions; this does not generalize well as it is heavily bothered by your offset curve endings, and the point-ordering of your curves. It is also a solution from 2012, which is nearly a decade ago
So, I’d like to ask, what is the best way to robustly (i.e. variable line thickness, graceful corners and rounding, invariability of results if points in the curve are reordered…) to turn what’s on the left to what’s on the right?
I can do just this with Illustrator, but giving a complex set of curves a link thickness, then “expanding” and using the “stroke”. Obviously, I’d like to do this without illustrator!