This just came up in a campaign I was in, DM needing to create a room on the fly but accidentally moving the map tile and revealing unintentional areas, which begs the question why don't we have the option for the DM to freeze the game map so edits can occur and then release that update to the players? During this time he can move tiles, maps, tokens what ever needed to update a "room" because lets face it sometimes PCs go in places that they shouldn't. The DM could then click "Update" and the map would at once update to the current screen of the DM, or he could clear and the lock would be released. Just an idea! I know I would personally find it very useful.
