Let me ease your confusion, Supplyguy.  

The feature is only available in the Desktop version. As my colleagues shared previously, you can add the number to each line item in the description field in QuickBooks Online. It will help you get around your concern.

You can check this article on how to customize sales forms as a future reference: Customize invoices, estimates, and sales receipts in QuickBooks Online.

If you have additional questions, feel free to get back to this thread. We're available 24/7 to answer you.