How do doors work in skirmish couldn't find anything on them

It just takes an action while adjacent to the door to open them, and then you take the door off the board and it does not return.

Thank you, that's what we thought

It kind of bothers me that we can't close doors other than "Events"

There have been plenty of times that a group of storm troopers would have benefited from the first one opening door, taking shot. Second moving up taking shot, moving out. Third moving up and closing the door.

Plus it would then burn a hero's action to open the door. Helping with the action economy.

I miss closing doors like we could in descent.