Show a hidden map part with another color until it is visible
This can be used to show that map part as hidden but showing its shape, but not its text mesh. For this, go to the Map Tile Builder inspector and enable the option Use Other Color If Map Part Disabled (make sure the option Map Part Enabled is false).
In this case, a color field appears to be configured:
In the above pictures, this can be appreciated, on the left, the main hall hasn’t been found yet, and on the right, the player has found it with the map part trigger.