Control group

I have some issues with control groups.
Ex. I want my all my knights assigned to control group 4 AND half on 1 and 2 to flank.
So i want to have a quick way to move all my knights. But also be able to control 2 groups individually!

However, in AoE a unit can only be assigned to 1 control group.
I assume this is a bug but i was wondering if anyone knew a fix to it. If this is a feature it must be a way to disable it but I could not found it.