Thank you very much for your nice review and I'm really glad you are enjoying the game! I agree that the UI needs a lot of attention, and that it would probably also be more player-friendly if it were organised better. I think for smaller screens some UI-scaling setting should be easy to implement.
As for the nodes, yes, default placement of new nodes has to be improved and I thought about some kind of system for combining nodes into functions/macros (if that's what you mean by snappier) but the latter would have been beyond the scope of what I would be able to make in a month :). As for the stability: I'm not sure how much one can throw at it, by some miracle it never actually crashed for me with graphs of high complexity (provided all the connections were valid). Of course eventually GDscript reaches its limit in terms of performance and the framerate starts tanking (try 625 Terrabots). For the long term it would probably be best to move the instruction graph to C# and look at some kind of node-compilation techniques, but there was no chance of that happening by the jam deadline of course! Feel free to look at the source code and steal any parts you like (I'm hoping its possible to just import it into Godot, if that's not the case I'll look into it)