Thanks for reaching out to us here in the Community, @syoung.
I'm here to help make sure the quantity ordered list will show on Purchase Order in your QuickBooks Online.
Currently, customizing Purchase Order (like adding Quantity) comes directly from the Master Form Type Template, regardless of which template you have set as default. In order for the quantity to show on Purchase Order, you will need to make sure that this column is selected in your Custom Form Styles settings.
Here's how:
1. Click the Gear icon at the top, then pick Custom Form Styles under Your Company.
2. Select Edit on the right side of Master form type (or Standard form name) under Action.
3. Go to the Content tab, then select the middle Pencil icon on the right pane.
4. Put a check mark on the Quantity under Columns.
5. Click Done.
I also attached some sample screenshots for your visual guide.
Once done, you should be able to see the quantity ordered list on the Purchase Orders.
That's it! Please let me know how it goes by leaving a comment down below. I'd be glad to answer should you have any follow-up questions. Wishing you and your business continued success.