How do you add blank lines to an invoice?

Hello there, @shs0973.

1.  From the left panel, click the +New icon.
2. Select Invoice.
3. Enter the Customer info, and then the Products or Services.
4. Choose the Add lines button, directly below the Product/Service section.
5. Click Save and Send.

This article offers additional details on using invoices in the QuickBooks Online: Customize your invoice in QuickBooks Online.

Let me know if you have any other concerns. I'll be around to lend a helping hand. Wishing you well!