How do you Create working Hidden doors in the Fallout 3 GECK?

To create a working hidden door in the Fallout 3 GECK, start by placing a door item in your desired location. Set the door's properties to "Hidden" by adjusting its flags in the Object Window. Use a trigger box or a script to control the door's visibility, making it appear only when the player activates a specific mechanism or object nearby. Finally, test the door in-game to ensure it operates as intended.