Four walls, one file. Every prop is a row with a switch; flip one and it leaves the room instantly, keeping its copy. Adding a prop is adding a row: a name, a wall, a position, a line of dialogue. This is the same control an admin screen gives you after launch.
Walls 1 and 2, live. Wall 3 is switched off — its four props stay written and positioned in the room file, and come back the moment there’s art for them.