Hi EricST,

I know how you want the SKU column to show on your purchase order (PO). At this time, customizing your PO isn't possible. As an alternative, you can enter the SKU information on the Description field so you can email it to your supplier. Let me guide you through the steps.

1. Click the Plus (+) icon on the upper-left.
2. Under the Suppliers column, select Purchase Order.
3. Enter the necessary information like the Supplier's name, email, mailing address.
4. Under the Item details or Category details section, enter the item information including  SKU under the Description column.
5. Click Save and send to email it to your supplier.

Please see the screenshots below for your reference. 

If you want to know how to receive or pay part of a purchase order, you can go over on this article for your future reference: Create Purchase Orders In QuickBooks Online.

Let me know if you have other questions about QuickBooks Online. I'll be right here to help you.