Many game engines and 3d editors have some sort of node based editing system. There is a wide variety of applications for it, e.g. for materials, state machines, scene graph editing and even game logic.
It appears that the xenko developers already created a prototype internally and we also have a first proof of concept with our visual programming language VL up and running. You can read more in this GitHub issue:
Did anyone already use visual programming? What was your experience with it and do you want to have it in xenko and what would you like to do with it?