I will share with you my work-around to this gap in QBO.  Run a Profit and Loss by Customer report and filter for the Customer you need data for.  Set  "display columns by" to customers.  Then you will have a report showing all the expense account.  If you then click on the Total Expenses at the bottom of each customer you will get an itemized report of the expenses allocated to the customer. But you can only run the report for oen customer at a time because the customer name is not available to include in the detailed report. The expenses are grouped by expense account. If you want to ungroup them, you will have to export to excel and fiddle.