How to delete a category in the "applies to" area of the Discount set up page.

Hello everyone,

I have restructured my store somewhat, and as a result I have a large number of no-long-used product categories showing in the "Applies To" area of the discount set up area of my webpage, forcing me to do an inordinate amount of scrolling/searching to find those categories which still ARE in use.

How do I delete the obsolete categories from the Discount set up area?  I have already deleted the unused categories from the product pages.

Any help appreciated.

Sincerely,

David Doyle