Quote - Select one part, parent the other parts to it. Save to the prop library. Use the "select subset" option to select all parts during the save process.

But these items are separate props and they stay separate, when you load them from library. Only difference is that you can load them with one click.

If you wish have one prop with mobile elements you must export them as an obj, and later export the same elements in different positions, as a morph targets.