This is an incredibly simple problem for which a fall-over-simple solution is apparent to everyone but me.
I used the Split function to capture a series of arm and leg poses from a figure I animated via Mixamo. However,the basic properties for these extracted meshes are grayed out and can’t be modified. I also noticed that the original figure mesh properties are also grayed out, which makes me think it might have something to do with the skin component.
I googled “basic object properties disabled” and found several forums from the 2008 era that refer to a ByLayer/ByObject attribute in the Object properties as the source of the problem. But as I am blind as a bat, I can’t seem to find that toggle anywhere. And nothing popped up in the Help menu.
Model is here: https://adobe.ly/2WJlrHO
OK, laugh now and get it over with.