Very nice! I've used a spline tool in SolidWorks that I found useful and was hoping to find something outside of solid modeling that was similar and this seems to be it, super intuitive and clean!

Probably not the use it was intended for, but I wonder if this could be used to improve imagemap polylines. I use Wikipedia's imagemap tool [0] and I wish the interface was like this (actually, I use a separate site [1] to generate the polyline values).

[0] https://www.mediawiki.org/wiki/Extension:ImageMap

[1] http://maschek.hu/imagemap/imgmap/