Current questions and answers regarding the map editor.

SetObjectEnabled("cartograph", nil);

function cartographF(heroname)
------------- ... additional conditions ... --------------
        QuestionBox(GetMapDataPath().."vopros.txt", "voprosF");
end;

function voprosF()
         ------------ ... -------------
         OpenCircleFog(x, y, floorID, range, playerID);
end;
         
Trigger(4, "cartograph", "cartographF");

where cartograph is the name of the cartographer on the map, vopros.txt is the text message that the player will see when interacting with the cartographer, and voprosF is the function that is called when the player gives a positive response to the message;
OpenCircleFog(x, y, floorID, range, playerID):
x, y - coordinates of the tile around which the area will be "revealed"
floorID - 0 - surface, 1 - dungeon
range - radius of the area to be revealed
playerID - the player number for whom the area will be revealed.

P.S. There is another method in which the area is revealed on the corresponding region.