Regarding your OP -
Global - The object does not get destroyed when changing layouts.
Persist - The state of the object will be remembered for when you return to the layout.
To keep track of entrance/exit positions without a mess of global variables, here is what I recommend:
A single (can be invisible) entrance/exit object with an instance variable ID keeping track of pairs, and another instance variable with the target layout. Every pair of doors needs a unique ID linking them together.
When your global character sprite comes into contact with a door, it saves the ID of the door to its own instance variable, then gets sent to the new layout. On start of layout, place the character on the door with the matching ID. This will work both ways, and with any number of doors, as long as each pair of doors is uniquely identified. No global variables needed!