Hi Econ and thank you. This function is already available in Odoo 14, but this is for manually giving a discount for an order line.
I am talking about the promotion function. Certain customers get regular percentages on certain product categories for which I use promotions. This big customers like to order 50 or more items at once. After hitting the promotion button on the sale order, further order lines are added for each discount. Therefore the discounted amounts are summed up for each category. This is hard for a customer's accounting to decipher if we have granted them the agreed upon discounts.
Some customers use SAP and can print out the discount for each order line as a second line, that explains what discounts were granted for this product.
For consumers this is overkill, but I had to learn that bigger businesses insist on this.

I don't know how to reply to you even trying to click all the dot menu I can find. Odoo is really limited out of the box.

For your requirements, since I'm a developer, definately I'd add a small modules for detailed_discount and attach it to sale_order_line and modified some reports (like the quotation so that it is printed under each and every order line). This shouldn't be too hard to do especially with AI assisted models such as Claude Sonet. This is similar to the different tax applied on the sale order line. And it's for explanation and view only so it doesn't affect any other Odoo functionality. And then SAP lookup to Odoo and say: how could you possibly do that in a few hours?

If you don't want a whole more module and want to make it simple, I think we can create a html field like detailed_discount and with some python code to populate this field and then print this field under the sale order line. I usually create these html fields so that the sale person can double check on the items too, whether's it's discount, additional charges, related components etc.

Yeah, looks like it needs another custom app 😅. Thank you so much for your time and effort. I've recently written an app with ChatGPT4o. It turned out successful, but it was also an adventure. I'll have a look at Claude Sonet. Thanks again!