Disney has recently made a change to the Walt Disney World and Disneyland websites that offer easy access to any applicable discounts. There is now a “View Discounts” link that, when clicked on, will display any applicable discounts at the merchandise location.
As of press time, there are no such areas within the My Disney Experience app that surfaces discounts information on the merchandise location page.
Of course, if you want an easy to view, and sortable list of Annual Passholder discounts, you can visit the full merchandise discount list here: https://disneyworld.disney.go.com/passholder-program/passholder-benefits-and-discounts/merchandise-discounts/