Quick feedback:
There's a CSS / content bug on the sign up page. The google and github logos are present but no words. Screenshot: https://ibb.co/hRLvWy8
For me, the lack of keyboard shortcuts is a non-started for my immediate usage. I like to just slap stuff down and jump around vs spending time organizing and compiling. Mindmup is just as "awkward" with managing notes on nodes but the keyboard shortcuts are a real timesaver.
Have you seen Arrows.app?
You might find some additional inspiration looking at another tool I used from Jason Koo that also uses arrows.app for generating graph data:
https://www.youtube.com/watch?v=HxO835DKzKs
https://mock-graph-data-generator-app-fjbvtm7qtyvs3f4ddeerz7...
https://github.com/jalakoo/mock-graph-data-generator-streaml...