[SubiculumCode]

Your experience, I do not doubt. However, I believe you misrepresent what the authors are claiming. They do not claim that constraints are new, rather that setting all the constraints manually can be tedious, and tools that intelligently select sets of constraint options can be useful at the practical level.

[s1mon]

Many of the existing tools will automatically add constraints as you go. Certainly the tangent, horizontal and vertical constraints can be done while sketching with a tiny amount of care. Some systems will look for other circles and try to set equal diameters. Most systems have shortcut keys which can be used to quickly set missing constraints - taking a similar number of clicks as the UI shown in the demo video. I hope there are cases where their tool is faster or smarter, but it wasn’t evident from the demo.