I have found that sorting by parent COU on the COU listing page does not seem to work. I have attached an image right after I tried to sort by parent and it looks like it is still sorting by the COU name (first column).

Also, I'd suggest that in the filtering option to filter by parent COU, the drop-down selector should be limited to only COUs that are parents - i.e., have children.  We have many COUs but few parent COUs and searching thru the dropdown list is tedious - well over 100 entries.