If I have all of the assemblies loaded as lightweight, I have to scroll down to the bottom of the assembly to find the primary planes for the assembly. I can't remember if this is the way it has always been. I haven't work with lightweight assemblies for a while but in order to pick the planes to create mates in the main assembly, it makes it very hard to find the planes.
Assembly loaded lightweight:
Is this how it is supposed to work or do I need to send in an enhancement request??