GUI Curved Line in RealTime (not editor)

Hey guys, am trying to build this (Simple node editor - Unity Engine - Unity Discussions) and want to learn how to do this without using Editor dependencies e.g. Handles.DrawBezier.

Am looking to make a visual scripting interface for a small game. I am using Rect/GUI.Window in onGui() to create each node. But how do you implement Bezier curves in GUI? I want to implement this in the deployed exe (windows runtime), not the Editor window.

What is the best way to do this?

Under the hood, Handles are just doing a bunch of GL calls