Hi totalmach1.
Saving time is the name of the game and being able to duplicate invoice templates would help achieve just that. I'd be happy to help go over how to make an invoice template in QuickBooks Online.
At this time the only way to make a duplicate template would be to either recreate it from scratch or manually import it into QuickBooks Online. In order to create the template from the beginning you'll need to go to Gear>Custom form styles>New. From there you'll just need to change the information in the template to match the existing one. In order to manually import a template you first need to have a template created to upload. Once you do you can follow the steps in this article on how to upload the template to your QuickBooks Online.
If you have any questions let us know and we'd be happy to help.
