How to use two different sort-by menus

[KonAntGR]

Hello, I'm faceing a serious problem I'd like to solve before I launch my e-shop.

In my online bookstore I'm going to sell both new and old books. 

I've made 2 different pages, one for New books and one for Used books, and two different sort-by menus, but it seems there's no way I could use both sort-by menus, one for each category. I want to use one sort-by menu for New Books page and one for Used Books page, but Shopify allows me to use only one of them.

As you can see from the screenshot, when I try to customize my theme, I only got to chose one of them.

Is there a solution to this problem? It is critical for the whole business of mine.

Thank you!

[gcelu]

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i think you need to make use of the collection section for that

[KonAntGR]

But I already make use of the Collections! 

Think of this "map": a sort-by menu with 15-20 collections (aka different book categories), but I've doubled those collections, one for new and one for used books page. 

I need one sort-by menu for the collections (book categories) of the New books page and one for the Used books one.

In this screeshot (ignore the Greek language, they are just Collections-Book Categories) you can see all the collections of the sort-by menu for New books (in the New books page). I just need to add another one to the Use books page. When I try to do this from the Customize enviroment, it changes for both pages.