I gave this a quick shot and failed as well. What I can say is that using invisible helper sprites as pinning assistants didn't work out in the end, and if I were to attempt again I would definitely utilize families, probably not rely on the built in behaviors, and use an instance variable to keep track of groups of pinned objects.
The good news is that the pin and drag drop behavior are both probably among the easiest ones to recreate by events.
Scene graph hierarchies may also possibly be of use here to keep track of groups, but I unfortunately have zero experience with those yet so I'm not sure.