How to use External Layouts

I’m creating a game in which I’m using External Events as functions and scenes as levels.
My game has 60 levels it means that there is need 60 scenes. My games logic remains same only the map/stage design changes.

Problem is that by using 60 levels the size of game file (code.js) increases as I add more and more scenes I want my game under 5 MB but This approach is not good.

I think External Layout can help me our but not know how to use them and what are they.
Any example will be appreciated

External layouts are basically the same as a normal scene just without any logic attached to it.
You design a level in an external layout and in the game scene you drop all of the external content onto the scene by using “create objects from external layout” action. Just be sure to put all level specific objects from the external layout into an object group so that you can get rid of them alltogether when you switch to the next level.