Jonathan,
thanks for the clarification, I indeed misunderstood the new tag. On the other hand: not all (related) selection issues are tagged as such, are those in danger of not being fixed for 9? Anyway, all of them _could_ be fixed in one stroke by throwing away the evil MultipleSelectionModelBase, particularly its usage of ReadOnlyUnbackedObservableList which forces those ominous manual change notifications (which are not trivial to get right). Instead, implement a bitset-backed observableList with the available (since 8, very sound in my experience) collections infrastructure that does all the heavy lifting plus a coupled (kind-of transformed) items list. You know where to find a POC replacement :-) CU Jeanette