RE: Billing Transaction in Workbooks
Billing transaction is a specific type of join (in saved search, it would be an Applying Transaction where the Applying Transaction Link Type is Order Bill/Invoice)
You will have to do something similar in your workbook to get something like the billing transaction. You probably want to get familiar with the help at: https://system.na0.netsuite.com/app/help/helpcenter.nl?fid=section_1543418452.html.
The join you are interested in can be found at Transaction> Transaction Line> Related Transaction Lines – Next.
At the very least, you probably want something that ends up looking like: