Input field with Simple Type

I have created a input field which is connected to a value attribute which is connected to a simple type with pre-defined values.

I want to fill in a free value (not in the simpletype) in the input field and save. But the app doesn't accept it because it is not in the allowed values. Is there a possibility to solve it, so I can add a free value?

If the question is already answered, I am sorry but i cannot find it.