Hello, JEM-SY. 

Yes, you're correct, that's how it works. The vendor credit won't be added without any open bill. Thank you, and I appreciate your feedback.

You'll want to check this article about managing the bills and their payments in QBO: Enter and manage bills and bill payments in QuickBooks Online.

If you need to run particular reports for your vendor, please refer to this article for guidance on how to run and customize the report: Customize vendor reports.

Please let me know if there's anything else I can do for you. I'll be standing by for your response. Take care.