I am doing some testing in the Purchase Contracts module, specifically tdpur3107s000 Maintain Purchase Contract Discounts. When I open tdpur3108s000 Maintain Discount Parameters by Contract Line, it does not give me an option to select "Cumulative" as my discount method. I tried every combination of 'Discount on Order/Line Item/Both' and 'Grade by Quantity/Amount' but the discount method is always stuck at "Parallel".

Any suggestions?

Cumulative and Parallel matters only on multilevel discount. If you need to make it cumulative the discount level should be more than 1.