I don't know if this can be done with the current maps. Is there a way to indicate a tunnel or cave path on the current map; or even be able to bring up a sub map. Maybe it could be some type of overlay on the current map.
Many major tunnels we already have separate maps for. The expansion is new and its gonna take awhile for new maps to come. It takes people a lot of time to map things. Also those mapping usually put priority on major zones over tunnels.