How can I add Groups using Formatting model utils to build a formatting settings model?

Hi there!

I use Formatting model utils to build a formatting settings model to populate the property panes. There are models, cards, and slices.
I have relations as "Model -> Cards -> Slices". I want to add Groups and then it should look like "Model -> Cards -> Groups -> Slices". 

I found some information about the Formatting group here and I found an example of how to generate groups using "getFormattingModal" here. Then I should use getFormattingModal for all my formatting settings and I don't want it, because it is not convenient.

So, how can I add groups to the formatting model using "Formatting group" instead of "getFormattingModal"?

I need something like this: