plinkie could you further talk on this of you have the time? A couple weeks ago I tried to the same thing but failed. Imagine an enemy in the secret place you want to "find path" and "check for collisions" with other elements in the secret place. But since the secret place is on another layout no one is moving until you go to that layout, even if you include it's event sheet? So you can "goto secret place layout" but then main "layout" stops, and you just can't run both of them together.
The way to solve this was to mathematically model all the behaviours and events in both the secret place and the main area in an event sheet, and update each tick. Upon entering the secret place you draw secret place objects, and upon exiting you draw normal place objects.
Which was borderline impossible/unneccesarily long to implement and debug.
v00d0, what I did to solve my problem can be described as:
1-)Use a large layout
2-)Use a global variable to keep current location ie outside, inside secret place
3-)Place your secret place sprites somewhere in the layout, way far from outside sprites
4-)Define camera limits for outside and inside
5-)Switch player location and camera when entering/leaving the secret place.
I hope I could describe it :)