For now, QuickBooks Online can't copy an invoice to a new credit note. However, we can link a credit note to an invoice.
Select the Plus icon (+) at the top, then choose Receive Payment.
Complete these fields as follows:
Customer - From the drop-down list, select the customer the credit note is for.
Date - Change if necessary.
Payment Method, Ref#, Deposit to, Amount - Fields are to be left blank.
Memo - (Optional)
Select the Credit Note that you are wanting to apply to the invoice
Verify that the total to pay (if any) is correct after applying the Credit Note.
Select Save and close.
It would be great if you can also submit a feedback for this one through the Gear icon then select Feedback. We have a product release every month and most of the enhancements come from the customer's feedback. As we strive to become the most user-friendly accounting software, your voice really matters.
If you have questions, please let me know. I'll be happy to lend a hand.