Multiple Layers

With the click of a button your level is copied into a 2nd layer wich you can then alter further as you wish.

I imagine a nice city that has its layer copied and then I alter much of that city since it will be damaged from the attack of a goblin army. Much is in ruins and the heroes wich first enjoyed a fine day and spend the night at an inn wake up to the alarms of that the city is under attack.
The 2nd layer kicks in instantly and without having to make a 2nd saving.
This will be more and more handy the more layers you need. Very nice if it could be within same map file.

For reference: Dungeondraft uses this feature