Oh, you're using sprite shaper 😮
Can't say I've ever used it, but it seems to use either a Polygon or Edge Collider, right?
I'd say the same advice would apply. Just break your level into smaller chunks (i.e. have a game object for the spawning area, another for the slide, another for the ceiling, etc.).
About my stairs you shouldn't worry about. I thought you were using a tile map.
This by default gives you a grid of colliders for every tile (very bad and not supported by my asset) and once you use a Composite Collider (very good and supported by my asset) you end up with the shape you saw on my first reply.
If your setup is causing you problems maybe try using an Edge Collider instead of Poly? (dunno if your character might fall through if framerates go bad tho)
Just remember to refresh the colliders every time you update your shape.
Don, sorry 💦