How to edit colliders with the cursor in game mode?

How to edit colliders with the cursor in game mode?
I want to simulate the path of a waterfall in a game.
It’s a bit like the android app “Sand Balls”.

Which colliders types do you use? What do you mean about editing? It can be scaling, shaping or mesh collider changing

I mean mesh collider changing!
And I want to “reverse paint” a mesh with a collider at runtime.

You can edit MeshCollider.Mesh as usual mesh: https://docs.unity3d.com/Manual/class-MeshCollider.html
https://docs.unity3d.com/ScriptReference/Mesh.html