Promotion planning and lowest level KF

Hai,

The promotion key figure has to be the lowest level of detail, which means the KF has to be the lowest in the hierarchy. This means, I can only assign promotions at the lowest level?

For example, a product called DOW white color soaps and a group level called DOW soaps. So as per the promotion planning, I can only set promotions at the DOW white color soaps and not at the group level of DOW soaps? is that true? What if I have a case that I have to specify a promotion at group.

Thank you.