That's a great question, @mjconnors.
Yes, you can add a filter to any reports in QuickBooks Online (QBO) except for payroll reports. Let me show you how:
1. Go to the Reports menu at the left pane.2. Choose a report.3. Click the Customize option at the upper left.
4. On the Customize Report window, you can select or add any filters on the Filter section.5. Hit Run report.
That should do the trick. I'm also adding this article that tackles how to customize reports in QBO for future reference.
Please let me know if you need anything else in the comment. I'll be happy to help. Have a great weekend.