Apps like Order Tagger, OrderlyPrint, or Order Automator can be used to automatically tag orders with labels like "Box #1," "Box #2," etc., based on the customer’s subscription cycle. The tags can then be included on packing slips and shipping labels.

These apps let you set up rules to automatically assign tags to orders. For example, if it’s the first shipment, it gets tagged as "Box #1," and the second shipment as "Box #2."

Edit the packing slip template in Shopify using Liquid code. You can customize the template to include subscription-related information, such as "Box #1," "Box #2," etc., if this data is stored as order tags, notes, or metafields.

For more flexibility, you can use apps like Order Printer Pro or Printout Designer, which allow you to create custom packing slips that pull in the specific box information.

You can use metafields or line item properties to store the box number information and have it show up on the packing slip or shipping label. Apps like Metafields Guru or Shopify's built-in metafields can help manage this.

When an order is placed, you can automatically populate a metafield or line item property with the box number, and this data can be used in custom templates.

If you’re on Shopify Plus, you can use Shopify Flow to automate workflows that update orders with tags or metafields, based on conditions like subscription cycles. This can be used to dynamically assign "Box #1," "Box #2," etc., to orders.

Flow can trigger based on events like subscription renewals and update order information accordingly.

An app like ShippingEasy integrate with Shopify and offer customization options for shipping labels and packing slips. You can set them up to pull in order tags, metafields, or line item properties that indicate which box to ship.