Hello, I don’t think that it’s easily possible to save a scene during runtime (not just in Edgar but in Unity in general). So I think your best option is to just freeze the current level (stop enemy movement, etc.) and hide it, then show (or additively load) the challenge level and when it’s completed, destroy the challenge level and unfreeze/show the original level.
For example, if you had the whole level inside a single game object, you could probably just disable it for a while, show another game object with the challenge level, and then go back to the original level.
But I don’t have any personal experience with this.