Do you leave your dogs alone together?

For those who have more than one dog: what do you do when you leave the house? Do you let your dogs hang out together? Do you crate them? Put them in different rooms?

I currently have a dog and a cat and am considering adding a second dog to the mix. When I leave the house, I always separate the dog and the cat just in case, so I’m just trying to consider logistics if I were to add a second dog.