Screen Host edit/create (Forman 1.1stable)

On tab "Puppet classes", "Avaliable class" I clicked to some group with two or more nested classes and there are two scenarios:

1. I clicked on "+" always to first one class in the list until it is empty
Result: I have chosen all of classes in the group

2. First of all I choose the latest one (as we suspected, it moves to Included classes), afterwards I'd like to choose the new latest one, but "+" is inactive, so I can't do it.