To change Channel Settings deactivate the desired Channel(s) by unchecking the corresponding checkbox(es) on the left side of the Config Panel.
Deactivating a Channel will make it unavailable in connected just:in User Interfaces and the channel will also disappear from the Channel List within the Connection Tab in the Inspector.
After changing the settings of a Channel you need to enable it again by clicking on the corresponding checkbox. You can only activate Channels with valid Video Modes.
Once the channel is activated/enabled, it will be available in the Connections-Tab within the Inspector.