In the parameters setting for the report exclude that particular expense category. Towards the bottom of the parameters screen click on "By Individual" then all categories will be shown in the selection box and you can exclude it.
Accounts Receivable, by definition, is a current asset...i.e., an
increase in Net Worth. AR is not an expense category by accounting rules.
I know, it might sound complicated, but I would set up _asset__ accounts
for each client, so that you can run a report by accounts of transactins..
When a "sale" is made, it is a reduction in inventory (another asset
account) plus gross profit (the difference between the cost of goods
(inventory0 and what you charged. Obviously, if you have labor, that
would be an expense that is increase and charge against the sale.
Payment of a "sale" would be an increase in Revenue, (an income account,
and a reduction in the account receivable.
Running a report by account, would show outstanding amounts (a positive
number, how much inventory uoiu have. A report of income and expenses
will should gross revenue, and constituent expenses.
... so same approach, but when you create the first txn just use an asset account as the category(transfer) field (instead of expense category) and then the same again with a negative amount for the receipt.