Hello there, @usersrstephentn.

Currently, we're unable to create a template with pre-populated line items in QuickBooks Online (QBO).

However, you can create your template and import it in QBO. You can check this link for more information: Import custom from styles for invoices or estimates.

I've also added this article about customizing estimates in QBO: Customize invoices, estimates, and sales receipts.

Drop a comment below if you have other questions. I'm always here to help. Take care!