Category search questions – subcategory order and/or hide

I’ve added the category to my advanced search. I have two tiers of categories. I selected the option to add the category on the main search bar, but it loses the category hierarchy when it’s placed there. (When I add this below the search bar, it keeps the hierarchy OK, but I’d prefer to have it in the main bar.) See screenshot – for example the Amusement Park SUBcategory appears above its parent category called Attractions. I assume this is a bug? How do I repair it so that the category hierarchy remains in tact?

Also, is it possible just to to hide the sub-categories from the search bar completely? So that only my top level categories would show in the drop down?