Add alpha filter for new product field

[yakbuttertea]

Does anyone know how to add a new alpha filter on top of the product listing page to sort by a new field in the product table?

Or how to make the existing alpha filter sort by the selected column on the product listing table?

Thanks

[yakbuttertea]

Does someone has an idea on how to do this?

[yakbuttertea]

A last attempt to find some clues in how to handle alpha filters. It seems that the alpha filter is only linked to the products name field, so my question: is how to change that to a different field?