We're taking notes of your feedback and suggestions, @userinfo115.

The item-wise discount is currently unavailable in all country versions of QuickBooks Online (QBO). Please know that all suggestions are being considered by our product engineers based on the volume of requests and their influence on the user interface before they are implemented.

As an alternative, you can manually enter the amount of the discounted item per line. I understand the item-wise discount option is beneficial to you and your business. This way, your work will be easier and faster. 

For now, I encourage adding your vote here in the link. This way, they can further review the request and consider adding the item-wise discount option to all country versions of QBO. You can also go to this feedback forum to check the recent updates in QuickBooks.

I'm still open to your replies if you need more assistance creating invoices in QBO. Have a great day ahead!