I have a modelled piano hinge where I left the concentric mate rotation unlocked so the hinge parts can rotate. When I place that hinge subassembly into my main assembly, it no longer rotates.
Any way to carry over the freedom of movement?
Make the subassembly flexible in the top level.
Exactly! How do I do that… 
Ok, replied before the picture! 
It seems like every command I assume to be available (like make flexible) are the exact commands that someone decided didn’t need included in the contextual menu. sigh
Thanks for pointing out the button.
Now open up the contextual menu and right click in a blank space. A “customize” icon pops up so select it. Now you can find and drag in any command icon your heart desires.
