finally figured this out after TWO HOURS with QBO tech support on the phone....... you have to go to the top right corner and click to view the invoice in the OLD view/version. Then your billable expenses magically appear on the right side of the page when in EDIT INVOICE (assuming you've already entered them in the EXPENSES tab and assigned them to the correct project/customer). 

It's worth noting, i did have to DELETE my original invoice that i had attempted to make, create a NEW invoice, click the 'old invoice view' or something like that in top right corner. 

You guys are not alone.