Thank you for responding. In regards to this:

With the new layout, you need to press the Tab key twice (after entering the details of the previous item) to add an additional line item. 

I'm unclear what you mean by "press the Tab key twice". If I press the Tab key after finishing the line, it jumps out of the invoice and to the "add lines" button. If I press it again (twice) it just jumps to "clear all lines" button. And so on. It just keeps going through all the other buttons and fields outside the invoice. In other words, pressing the tab key twice doesn't add an additional line item.

Again, thank you for taking the time to respond. If you have additional advice I welcome it. In the meantime I have already engaged with Customer Cares and Quickbook Cares. So far that process hasn't been helpful, but I'll keep trying.