Filtering dropdown list by product categories

So I want my dropdown box to fetch the names of products that are only sorted into certain categories. In the Stores/Products collection there is a multi-reference field name called ‘collections’ which are the categories that the products have been sorted into.

I’ve been trying all sorts but just can’t get it to pick up on the names of categories in the collection field. I wonder if it’s because they’re not displayed as text but more as icons? I’ve attached a screenshot of the collection field inside Stores/Products.