OutlineGroup enabled List, is it possible to bind a key path for expanded state?

Currently the new addition to list has a children: {keypath} to react to child > parent state, I am unable to find a expanded state binding for list with outline support.

How can I restore the expanded state in List with OutlineSupport?

Will this support be added?
Please! +1
OutlineGroup enabled List, is it possible to bind a key path for expanded state?
 
 
Q