A minimap accessible from anywhere is currently infeasible, but if your use case is only for something like admin, then there is a way to make that.
For setup, place a zone that stretches to the walls in each room you want updated with player activity. Also, in another location outside of your map, make a mini duplicate of the map which is small enough to fit on one screen. This will be the minimap the player using admin will see. Finally, add a waypoint in the minimap room and one near the table in admin.
Wire it up so that when the player presses a button in admin, they are teleported to the minimap. Make sure they can’t move around or use a camera zone to ensure they are always looking at the map. Then wire another button in the room so that they can teleport back to admin. To make it so the player can still be seen in the main map and get killed by the imposter, wire it so that a placeholder prop or friendly sentry is shown as soon as the player enters the minimap. If the imposter kills the placeholder, then the player in the minimap dies as well. And voila, there’s your minimap.
Additionally, if you want to add the functionality of the minimap to show which rooms have players in them, use the zones made earlier to detect if rooms are occupied and update the minimap with that information using text boxes for each room. I suggest using this emoji to represent a player 
. Hope this helps!