Hello there, @mauibrakesupply. We'll help you add a line between two items in your purchase orders inside QuickBooks Online (QBO).
When you create a purchase order inside your company, once you've added an item, it'll show you a + button that lets you add another line item to the transaction. We'll write down the steps and provide a screenshot to help you go through:
Access your QuickBooks Online company.
On the left navigational bar, click the +New button.
Select Purchase order.
Enter the necessary details.
In the Item details section, add an item and click the + button to add another line.