Why do I not see my existing collections in the Add Existing Collections list?
Shopify offers two different types of collections, Custom Collections and Smart Collections. Categories by BTP uses Smart Collections to define your category hierarchy. If you do not see one or more of your collections in the Add Existing Collections dialog, they are most likely Custom Collections. You will need to create new collections, either through the app or through Shopify's interface, in order to add them into Categories by BTP. Once these collections are created and added to the app, you can bulk add the Categories by BTP tags to the products in your old Custom collection by following these steps:
1. Obtain the Custom Collection's id by opening the old collection's edit page and copying the number at the end of the URL in the address bar:
2. Go to the products page and append the following to the URL bar where <id> is the number you copied in step 1:
3. Here, you can select all products, click under Bulk actions, and choose Add tags as shown above.
Once you add the tag to the products, they will appear in your category.