https://www.zoho.com/crm/help/sales-orders/create-sales-orders.html

However, the information given doesn't work.  According to the instructions, little arrows are supposed to appear to allow editing of the discount (and tax), but no such arrows appear for me.  Discounts are different each time a product is sold, so the discount needs to be able to be manually adjusted in a sales order.  Please tell me how this can be done.