Scenario: If I enter a value in "Discount %" after entering value in "Rate" field then the field value of "Rate" is getting removed automatically.
Solution: It is not possible to set multiple options for up or down the sale rate of an item in Price List. This feature will work only with a single option defined in a single item. If you try to set two options together like Rate and Discount then it will remove the older one always automatically. Now if define Rate then all the childs will be sold on that rate, if define discount then entire childs with different rates will be sold on same discount.