1.  Make sure your different servers are up and running, and that you can see them all at the same time from your in game server browser.   2.  Add a new path to the docker settings for the Cluster directory.  This should be pointing to the same directory for each of your servers:       3.  Add the Cluster ID and Cluster Dir Override flags to your Extra Game Parameters field.  I use "call1" for my Cluster ID, but this can be anything you prefer.  My flags