One should be able to create a relation in order to produce the following hierarchy:
  public class MainObject
    {
        public ObservableCollection<LibraryObject> ListOfLibraryObjects { get; set; }
    }
    public class LibraryObject
    {
        public string LibraryName { get; set; }
        public TrajectoryManager TheTrajectoryManager { get; set; }
    }
    public class TrajectoryManager
    {
        public ObservableCollection<TrajectoryData> ListOfTrajectoryData { get; set; }
    }
    public class TrajectoryData
    {
        public string Name { get; set; }
    }

WORKAROUND:
    public class MainObject
    {
        public ObservableCollection<LibraryObject> ListOfLibraryObjects;
    }
    public class LibraryObject
    {
        public string LibraryName { get; set; }
        public ObservableCollection<TrajectoryData> ListOfTrajectoryData { get; set; }
    //    public TrajectoryManager TheTrajectoryManager;
    //}
    //public class TrajectoryManager
    //{
    //    public ObservableCollection<TrajectoryData> ListOfTrajectoryData;
    }
    public class TrajectoryData
    {
        public string Name { get; set; }
    }