Bulk set preferred category?

When I export a list of items with the standard "category" field as one of the export fields, I get empty data for all items without a preferred category.

So, just working with items with only ONE category for online display.  If "item A" has a preferred category and "Item B" has a category BUT it isn't marked as preferred, then only "item A" will have data in the "category" column of my exported file.

Is there a way to mass update all items (in only ONE category) so that the existing category = the preferred category?

Also, is there a different column I can put in my export.  The "category" field appears to actually pull only the "preferred category" data.  is there another field that will display ANY category data (preferred or not)?