How do I get Vendor report to show both Bills and Payments all at the same time?

Greetings, @Rizzie.

You can generate and filter the Transaction List by Vendor report. It displayed all your vendor-related transactions grouped per Vendors. Let me guide you on how to do it.

1. Go to the Reports menu.
2. Scroll down to the Expenses and Vendors section.
3. Double-click on the Transaction List by Vendor report.
4. Click the Customize button.
5. Set the report date range from the General section.
6. Expand the Filter section.
7. Mark the Transaction Type tick box. 
8. From the Transaction Type drop-down, choose Bill. 
9. Click the Run Report button. 

Keep me posted if you have other questions or concerns. I'm always here to lend a hand.