Term1 is not available to set value for Term2:parent

Hello,

I have a Rule Set, which calls on Entity Creation. In this Entity i have a field_category (term reference) for Term1.
When node was saved, it creates a new Term(Term2), and should put it under the Term1 (Term1 as parent).
So i thought that it should be easy, just set Term2:parent = Term1. But it isn't. I can't select Term1 as value, when i go to -> Action -> set data value -> Term2:parent -> ? Term1 ?. No there is only the Term1:parent but not Term1 itself.

I think it's so, because Rules need a List as possible value, but Term1 isn't a List it's just value for Rules.
So, can we call it a bug? Or maybe it is a needed validation feature.
And what's about my problem, how can i put my new Term(2) under Term(1) in the hirarchy?

Thanks a lot!
the dropfen