In Sales Invoice, I can either apply one discount to entire invoice using “Additional Discount Option” or apply a discount to price list.
Practically, esp for small businesses, sometimes different discounts need to be applied to different items. Also, frequently small businesses do not have a standard price list rather they enter a rate and then apply a discount. to show to customer that s/he has been given a discount a discount may be applied to that rate. E.g. business ABC does not have a standard price list. A customer walks in and he is quoted price of USD 100 for product A and USD 50 for product B. After negotiations it is agreed that s/he will be given 20% discount on Product A and 10% discount on product B. Now since there is no standard price list the user needs to enter the rate and show discounts respectively on invoice. Currently this is not possible in ERPNext. I would request to de-link the discount field from price list rate and rather apply the discount to the rate field. The rate field is anyways updated based on standard price list where available.