I would make one event sheet for your general gameplay logic (which doesn't change drastically over different levels), one event sheet for pause menu, main menu etc, you get the idea. In the different levels include the general gameplay logic in a new event sheet for the current level and put only things inside that is different in this level, like a special enemy behavior.
What you can handle in the gameplay logic sheet: Score System, Pause System, Collision with enemies, collectables, game mechanics like teleporters etc., everything that works the same in every level.
Also make heavy use of families (for examples all enemies with similar behavior can be one family), put code in logic group units and comment your code, so you always know what a specific block does.