I have noticed that Masks remain the same when you change maps. So like if I have a map cut up into sections for easier usage and I go from the edge of one map to the other - the mask stays the same. It would be nice if the Mask was saved along with the map file so that when you go back and forth you don't have to completely redo the mask (which can take a long time to do). Instead, it is loaded in after the map is loaded. The GM can always reset/clear the Mask if they are ref'ing more than one game. OR - they could just rename the mask file. If the file is not present - it is just created. If it is - it is loaded into memory.
Here is an example of a map (yeah, I know - it is from a VERY old game). I've annotated it with ideas and would like to swap in/out those other maps. But if I did so, then the mask would have to be redrawn each and every time.
BTW: This is the starter dungeon in my game. It allows people the chance to try out their characters, make changes as needed, and to enjoy wandering through it. Once they reach a certain level they should be able to get out of the dungeon and into the game itself.
Heh. I just noticed that this is an early version of what I've done to the map in Visio. It is quite a bit more elaborate now than in this picture. :-)