Cloning a Pantheon Multidev Environment

It’s been a while since I’ve had to do this (I’m usually cloning off the master branch) but this weekend I had to duplicate a feature branch environment. I was confused because Pantheon’s only option as a starting point for the new multidev environment was the dev (aka master branch) environment—it wouldn’t let me dupe the multidev environment that I wanted.

After trying a few things I figured out that I had to use dev as my starting point to create the new multidev environment, but immediately after it was created I could clone the database and files from any environment, including the other multidev environment I wanted.