Thank you @zipit for your comprehensive response, especially with the link to the coding guide. I guess it might be better to create the spline manually from the points which are connected by the edges without the usage of SendModellingCommand. It was good for prototyping functionality but as you mentioned, it is hard to debug. I appreciate you took the time (and I know it's a lot of convoluted code) to read through it. @r_gigante -> the work is currently on my side so you don't need to bother. I think I have enough information to do a second iteration and rewriting this from scratch.