Thanks Andreas for responding,
In our scenario firstly we are providing the discount to the customers, Later if we get any add on promotional discounts from vendors we want that to be benefited apart to the customer as well, this is the place where second discount is coming into the picture.
Tried editing the existing discounts but the case is we have multiple combinations for discounts(item to vendor, vendor to group of items) hard to pick the existing and edit them. Because of "find next" enabled system is accumulating the discounts which is not apt solution to us.
For second parameter as mentioned that is working in a case if line and multi line discounts exist - our scenario is all are line discounts.
Upon any suggestions please post back.