Hi CrystalK, 

Thanks for joining the thread. 

QuickBooks Online allows you to edit the customer name to become the project however if an invoice is paid or has linked transactions, you'll need to remove it first before you can edit it. Let me show you how to do this in QuickBooks Online.

To delete an invoice

1. Open the invoice.
2. Click More on the footer and select Delete.

To edit a quote

1. Open the quote. 
2. On Customer drop-down menu select the Customer: Project name. 
3. Once you've confirmed that the details on the quote are correct, click Save.

To recreate the invoice from a quote

1. Open the quote.
2. On the upper right, click Create invoice. 
3. Select an option on How much do you want to invoice?
4. Select Create invoice.
5. Details on the quote will be added on the invoice. Select Save.

Before you create a quote or invoice, make sure you've selected the correct project of the customer. Or you may also create these transactions directly on the Projects tab. 

You can also check on this article for your reference: Add existing invoices to QuickBooks Online Projects. 

Feel free to message us back if you have any other questions. Have a great day!