Hi there, cmruble. I know how you can find bills linked to your closed purchase orders in QuickBooks Online.

There are a couple of ways to get your desired data. First is by running and customizing the Transaction List by Vendor report. Here's how:

1. Open the Reports menu from the left pane.
2. Enter Transaction List by Vendor from the search bar.                                                                                                                          
3. Select the necessary filters.
4. Click on Customize.                                                                                                                                                                                       
5. Under the Filters drop-down, check the box for Transaction Type.
6. Mark check the Purchase Order field.                                                                                                                                      

Second, you can view it directly from the PO page:

1. Open the Expenses menu and select Expenses.
2. Locate the PO you want to review.
3. Click on the Action column and hit View/Edit.                                                                                                                                                                     
4. From the upper-right part of the page, hit the blue hyperlink below the PO amount.
5. You'll then see the linked bills.
    

If you want to save your report's current customization settings, see this for the detailed steps: Memorize reports in QuickBooks Online.

Keep in touch for more help with bills, purchase orders, or QuickBooks. I'd be glad to guide you through. Have a nice day!