Add a discount or down payment line after the subtotal

Several users have requested the ability to add a dedicated line to apply a discount (e.g., a percentage or a fixed amount), a down payment, or a credit directly at the end of the report, after the subtotal. Currently, the software does not allow these deductions to be displayed optimally without using negative charges or relying on external invoicing/accounting software. This feature would make it possible to present a clearer and more transparent final net amount to the customer on the quote.