Criteria field

Hello everyone
I want to know your point of view of this component.
The project is being done in a system where the user can do a lot of querys about demographic information and can also combine them, store them and mix to generate their own querys.
My problem is this....
I have a list of criteria that can be unique or can be a group and the number of criteria is relatively long but the vertical space is fixed thats why it have the scroll. My problem is that I can not clearly differentiate the grouped criteria and unique criteria, and people think everything has the same level.

any suggestions?