When you add or edit a system connection from one instance of System Administration & Diagnostics, that connection is immediately updated in the system connections configuration file. All instances of System Administration & Diagnostics watch that file for any changes. When a change is detected, the changes are merged into that application's system connection list.
If the changes are unrelated to the application's active connection, no further action is necessary. If there are changes to the active connection that would require a reconnect, the reconnect is done automatically. If the active connection is deleted, the connection will be disconnected and no other connection will be established.