Seems a lot of people are struggling with Library assets for various reasons. I think this feature is massively under developed for what should be a great strength across Adobe applications. I still have Illustrator V17 in use as the Library works better than the current version for me, so my subscription is wasted money. I've complained before but to no avail. I create many line drawings with common line segments, so I drag these in from the Library, which creates consistency and should be time saving. Currently each one option-dragged no longer remembers the layer it came from and is a group, so you can't join 2 library items with a new path unless they are ungrouped! Come on developers - help us all out!