Can you customize a report to show discount amounts for each transaction?

Yes, we can guide how to add discount amount column in a report to show discount amounts for each transaction. Please follow the below steps:
Step 1: Open that report in which you want to add discount amount column (e.g. sale/purchase list/ account/inventory register)
Step 2: Click on the Custom Column option which is available at the top right on the report
Step 5: Then enter the name of the format and then press enter
Step 6: After this click on Add new column/row
Step 7: Enter the column title(Discount Amount), then specify the position after which column you want to add the new column
Step 8: Select the data type and then choose alignment and enter charcter
Step 9: Click on the data field and then select the category from which you want the data to appear in a new column
Step10:Click on filed & select then field accordingly(BS1,2,3_amount if you are enter diecount in bill sundry and if you are using item wise then you have to select DISCOUNT_AMOUNT) and then save field & then save then column 
Step 11: Re-open that report with new created format. 
or 
you can refer our item wise discount report of inventory summary fm display menu.