That's an interesting idea, although the optimal path for most levels skips checkpoints so it might not be very useful hahaha
I've thought about a level editor, but the code is already open source here: https://github.com/eboatwright/Speedrunner2
So if you just install the Godot game engine, (it's only like 300 MB) you can make and share your own levels :D
But I think I'll come back and add a few more levels to this game, and I think T had requested ice physics a couple months ago, but I've had another idea for a speedrunning game that's slightly different than this, but it would be way more feature complete and I'd probably add a level editor to that one
Another question: do you play in the web version, or have you downloaded the client?