Building a map that has no underground train tunnels.  Would it be possible to strip the train tunnel icons off the map from monuments without using breakable monument prefabs?

No, the train tunnel entrance map markers are part of the map. If they were distinct map marker entities, then plugins could simply destroy them. There might be a way for a tool to process your map file to remove the markers, but that probably won't work if the markers are part of the monument prefab (you would need to break the prefabs).

Ok thanks for the info!

KingSizeKevin

Ok thanks for the info!

can you change the status to solved (even if no remedy)  :)