The Category code on the item controls the Sales and Cost GL accounts when Day End Processing is performed. If you want to re-redirect which GL Accounts are updated by a credit note you can edit the Category code on the credit note detail and change it to a different one, set up with the desired 'quality' GL accounts. When Day End is run, both costs and sales GL accounts will be read from the new category.

The same logic applies to invoices as well as credit notes - the category code can be overridden in order to redirect the GL accounts being updated by Day End.