See here. Downloaded train track map from a console, and voila! I now know there were some college kids in the tunnel. Needless to say, I’ve never visited any of adjacent tiles, but very likely visited tiles that are above that mark. Working as intended or no? I guess no?
Marking draisines you find in the tunnels also puts their marker on the surface map rather than the underground map.
Auto map notes are filled when overmap tiles are generated. There is no check for visibility of tile with map extra. Yet.
Oh, that explains why the notes did not reappear after I… uhm… “changed” my character. Funny though that the auto-notes setting did get populated (only) after I rediscovered the tiles… which would imply that there’s a system in place to detect extra map tiles after a restart…
Great idea, but it seems it still needs some work.