You can't have more than one Desktop Application Group per HostPool.
"You can create as many RemoteApp app groups within a host pool as you would like, but you can have only one desktop app group within a host pool. A default "Desktop Application Group" is automatically created Whenever you create a new host pool, so you must remove the app group first if you would like to create a new desktop app group"
So either delete the one you have or if your goal is to have multiple you'll have to create a second HostPool.