When you have a large scale Magento store with thousands of products in every top-level category, dozens or even hundreds of offered filters for a single attribute in your layered navigation, certain necessities become mandatory – like selective attribute sorting. Even though Magento does offer sorting functionality for attribute values, in these situations that just might not be enough as you can not sort selectively for a specific category.
For instance, let’s say a customer is in a “First Category” and there he sees a brands attribute in layered navigation, filterable by these values:
A & A Specialties (1) Abella (2) Abex Friction Products (1) Absco Ltd (1) AC-Delco (166) Accel (1) Acco Ind (1) …
Then customer goes to a “Second Category” and again there is this brands attribute with exactly the same options offered to filter by.
Now, why wouldn’t you offer your customers filterable options in the order you find the most suitable, maybe boost sales by emphasizing a certain brand, or just sorted to be a bit more relevant to current category?