Using Paper you can update collection template to use tag based filtering. This is an easy way to surface sub-categories within a collection. For example, you may have a collection titled Accessories using nested navigation you could then set up links to Wallets, Phone Cases, and Bags.
Create metafield definitions
Open up Settings and click Metafields.
Click Add definition.
Set Name to Subtags.
Set Namespace and key to custom.subtags.
Click Select content type.
Click Single line text.
Click List of values.
Add data to collection metafield
Open the collection you’d like to add a tag filtering too
Scroll to the bottom Metafields area.
Enter a text value for each tag filter
There's no need to include "All" as that will be the first link within tag filtering
Each entry should match a tag that is present within your collection