I agree this seems like an easy fix for Quickbooks and it would make an estimate or an invoice actually readable. There is one template that does put a line in QB online called Fresh,  it puts the line in but with this template I can not do a summary of progress payments, I have to use the Airy New template to get the summery I'm looking for.   

My fix is I made a new product or service called Line. Then I put in the description a bunch of underscores until I liked how it looked.  Between every line item, I add the product or service called  Line and I delete the 0.00 price to make it blank.  Attached is how it looks. Not perfect but at least you can read it. 

There is a glitch in the templates that need to be fixed. Separation lines need to be added to all the templates and I would suggest having an option to have alternating color line items. Also, there is a progress payment glitch on all the templates I've tried besides the Airy New template. GET ON THIS QB!