I'm having an issue editing sub categories or sub-sub categories for individual listings after I search.

Category pre-selection in yellow below allows you to add a top, sub, and sub-sub level category prior to import to automatically fill that pre-selection into each search result to prevent the need to re-add to each listing before import. However if the sub or sub-sub category is not initially filled out completely as seen below again in yellow, the items will be empty as expected in each search result to mirror the preset selection.

If you want to add a sub-category later for each listing as highlighted in red, the system will show no results and not allow picking up the query at that point to add sub-categories. To retrigger the category query to add sub or sub-sub categories below, you must "start over" by reselecting the top level category again for that particular listing as seen in green.

To restart the query you must pick a different top level category to restart the selection engine. So if it is set as Category B for example, select Category A to trigger the engine then switch back to Category B again to the original selection and the sub-categories will now be triggered and allow adding the follow-on subcategories in red. So in short, either fill in the complete desired categories at the beginning or re-add the entire category structure individually as required using the process detailed.