Add Additional Shipment and Order fields in Checkout and Order Confirmation

After you click Checkout in the Shopping Cart, you will go to the Shipping Info tab. You may add more information e.g. PO number in the Order Information table, also add more fields like Reference Number and Notes for every shipment in the Shipping Info tab, the information you added in those fields will be shown in the confirmation tab.

Add and update the Global Checkout Shipping Fields

1. Go to: Setup → Custom Metadata Type → Field Set Definitions, add a Definition names Global Checkout Shipping Fields and the type is Checkout Confirmation.
2. Go to: Setup → Custom Metadata Type → Field Set Items, add the Field Set Items you want. The Field Set Definition is Global Checkout Shipping Fields and the object is Shopping Cart or Shipment.
3. If you want to add a field in Shipment object, please also add the field in Checkout Shipping Fields. For Shopping Cart object, it will automatically sync the fields.
4. Go to: Setup → Custom Metadata Type → Storefront → Manage Records → Global Settings, make sure Checkout Field Set is Global Checkout Shipping Fields.

View the Global Checkout Shipping Fields

1. Go to: Setup → Custom Metadata Type → Storefront → Manage Records → Global Settings
2. In Storefront Detail: Checkout Field Set → Global Checkout Shipping Fields
3. In Field Set Definition Detail, the Field Set Items are the fields for shipping and order which you can add.