There are a few ways to mass edit on Shopify. The easiest way is to use the Shopify admin panel. You can find the admin panel by going to your Shopify account > Settings > Customers. Once you're in the customer settings page, you can click on the Edit link next to a customer's name. From here, you can bulk edit all of their details at once. You can also use the Shopify app. Open the app and sign in.