i know there's a thread already for this but i couldn't find it so merge away if there is
now that carts can move with you on crossroads. is it too much to ask for crossroads to go underground? like 'connect to existing milestone' could be used on the mine entrance and right clicking on the entrance while underground now has 'extend xx' but no follow/travel along option on the tunnel exit/entrance and the extend option disappears after use/extended