Custom Target System Categories not editable for UNSGroupB

Hi all,

I try to use the feature "Group Inheritance Based on Categories" for a custom target system.

The definition of the categories in in the UNSRootB works fine (for group and account).

I also can set the defined categories for UNSAccountB.

But in UNSGroupB the control is always grayed out and cannot be edited.

What am I missing?