Hi narmdirector, 

I have two options for you on how to set a default invoice that products are already attached. You can either create a recurring invoice template that has an Unscheduled type or click a similar invoice and then Copy it.

Here's how:

1. On the left menu, select Sales then choose Invoices. 
2. Click the invoice transaction that you want to copy. 
3. The invoice transaction would open and at the bottom part select More and choose Copy. 
4. You can further check on the details and then Save and close. 

Reach out to me if you have other concerns. I am here to help you.