You're 23409712490 times better off just making your own level editor, to keep levels external. That way you can have all of them in a single layout; no lag.
Don't even need a level editor, just a method of saving and loading them. You can use Construct Classic's editor to handle positioning and sizing of each object, then have an "On start of layout" event which saves all the positions to the file.
This method is probably best for in-house level editing however, as it's faster but not so user-friendly since the players would need to learn to use Construct.
> I can't even use my latest project beuase of the lag. Ver sad.
You need a way to optimize the visible resources you are using. If everything is being constantly loaded into memory and stays there, then any game will bog down :)
~Sol
I think he means that he can't open his game for editing anymore Soldjah D=