Smileh
Another way would be to add another layer, or 2...set invisible - set objects collisions on that layer to disabled.
When your player gets to that exit, create a transition (like you would normally to go to next layout.) And then set the layer he just came from to invisible and destroy all the objects on that layout
Set that bottom layer to visible - objects collisions to enable.
It would be a lot of events and actions, but you could do this for a lot of maps.
If player is on layer "map bottom" destroy objects on "map top".
Then once your player gets to the exit to go to third map...create objects at their X and Y position. You'd have to put each object in the editor and record their position in the event sheet.
Event Sheet - Map 3
Player is on layer bottom - condition - player is overlapping exit box > System - create object > x on layout "map 3" at x and y position.