This switch is located at Channel>Channel Settings>Shopify Settings tab.
You can choose which category-based download mode will be applied to your Shopify channel. There are two options: (1) Get Category from Custom Collection or (2) Get Category from Product Type.
Selecting Custom Collection is usually preferred because, after you set up the conditions, future products are added automatically. You can save a lot of time by using automated collections if you have a large selection of products or if you have seasonal or rotating inventories.
Selecting Product Type affects only the products that you choose individually. Because of this, the collection always contains the same product type unless you specifically add or remove products. Based on Product Type collections take more work to maintain but can be a good choice for small or specialized collections that you intend to create personally.
IMPORTANT NOTE: This settings will be applied for the related Shopify channel.