Universal Containers wants to apply different Discount Schedules depending on the currency of the Quote,...

Create a Lookup Relationship on the Quote to the Discount Schedule for the user to populate.

Using a Price Rule, Inject the ID of the Discount Schedule sourced from a formula field on the Quote Line.

Modify the Discount Schedule formula field on the Quote Line to reference the IDs of your Discount Schedules.

Create a Discount Schedule for each currency in the related list on the Product.