vk12/vk13 to make mandatoryfileds in key combination to optional

When we go into VK11/VK12 for a particular condition(e.g. : PR00), I see some fields are mandatory for a particular key combination (eg: Sales org/ Dist channel /Division are mandatory entries) , I want to change them as optional(E.g.: only sales org should be mandatory but not dis. Channel and Division). How and where do I do it in configuration?

Please let me know if would be a great help.

Thanks,

praveen