You're already on the right track in monitoring your Purchase Order (PO) transactions in QuickBooks Desktop (QBDT), @whizzey. With this, I'll make sure you're able to balance the difference between the reports you've pulled up and keep your data accurate.

There's no need to create a new PO and then do a change order to check for any reporting issues. The Open Purchase Order report shows the total amount with the PO you've created and after the change order. While the Open Purchase Orders Detail report indicates the total PO amount excluding the closed ones.

Based on your screenshot, you'll have to either unchecked the closed POs or missing line items (please see the screenshot below for your reference) or filter both reports without the closed ones. This way, you're able to remove the difference between the two transaction reports and get the data you need.

Also, QBDT offers a wide variety of ready-made vendor reports that tell you where your company stands in terms of expenses and accounts payable. To further guide you in keeping track of your POs and inventory, you can customize your item reports by checking out this article: Customize item reports.

Please don't hesitate to comment below if you have other reporting concerns and questions about managing POs in QBDT. I'm always around to help. Take care and keep safe, @whizzey.