I closed my editor (WebStorm) and re-installed and everything works now. I did not get any warning previously though.
An extra mechanic of interest would be collapsing tunnels back to wall by attacking or dismantling them (only creeps, no UI). This could be done by an attacker to disrupt your supply chain or by the local player to defend against enemy incursions
@Atavus, I believe you refer to the usage of ramparts as constructed walls. I am asking for the ability to carve through terrain walls.
How about adding the ability to build 'Tunnels' on wall tiles, making them into roads. This should ease the road network in some rooms. Could be pretty expensive, though.