Hi there, @Q-B Online User 1.

As of now, there's no update on when this feature will roll out in QuickBooks Online (QBO). You'll want to visit our QuickBooks Blog page to learn some news and what's new in QBO.

In the meantime, you can consider the workaround provide by my colleague RCV to use the Memo or the Description field to add notes in the transaction.

Also, you might want to check this article for reference in case you want to learn how to customise your invoice in QBO: Customise your invoices, quotes and sales receipts in QuickBooks Online.

Don't hesitate to leave a comment below if you have other questions or concerns with your QBO account. The Community is always here to help. Have a great day and more success in your business!