How do I add sub-category links inside Template Header?
Shopify does not have a built-in sub-category system in place yet. That’s why we have to think about a smart way to allow this for merchants.
To allow this system, we parse through your navigation menu with the handle same as your Collection handle inside Shopify Admin > Online Store > Navigation:
For example, if you would like to create sub-category links for All products at url (collections/all), you need to create a navigation menu with “all” handle: