Larian Studios Forums Divinity: Original Sin 2 - The Modding Dungeon Divinity - Original Sin 2 - Modding General Hide Unvisited Rooms + Prevent Automatic Usage

Make sure you have the shroud enabled, I believe that setting is in Edit > Level Data.

EDIT: Oh and there are some problems with the shroud/regions in GM mode. I think they are disabled by Larian. You can search the forum for Shroud and probably find answers on that. I don't use GM mode.