Comment by Animats

Constraint-based layout works, but you need a serious constraint engine, such as the one in the sketch editors of Autodesk Inventor or Fusion 360, along with a GUI to talk to it. Those systems can solve hard geometry problems involving curves, because you need that when designing parts.

Flowchart-based programming scales badly. Blender's game engine (abandoned) and Unreal Engine's "blueprints" (used only for simple cases) are examples.