Thank you Buliak. It is not so easy to dig out Inkscape functionality from the code. Is there any code organigram or hierarchical tree or map somewhere?

Albert

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Please can anyone point to the source files responsible for the better Bézier node editing? I would love to have a good look at them.

All node editing is in src/nodepath.cpp and src/node-context.cpp, but it sometimes uses functions from src/livarot lib as well.