I have requirement, where business needs to apply discounts @ order line level based on customer DFF ( Saying yes or no) and Order DFF(%) modifiers should apply automatically the % based on the inputs@Order DFF and Customer DFF, once its applied, additionally, after the booking process, down the line if we are adding new order lines, user should not be able to apply any discount/modifiers ( need to restrict users)
I believe this would be possible. You'd have to create a custom pricing attribute based on the customer DFF to be used as a qualifier for your modifier. Then I would attempt to use the "Get Custom Price" formula to do the calculation based on the order DFF. I'm not 100% clear on the requirements you stated about restricting users later - if you set the calculate_price field to "Frozen" on the order line, the pricing for that line will not change.