[TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [FNiagaraHierarchyItemViewModelBase](API\Plugins\NiagaraEditor\ViewModels\HierarchyEditor\FNiagaraHierarch-_6) > AddNewItem ( [TSubclassOf](API\Runtime\CoreUObject\Templates\TSubclassOf)< [UNiagaraHierarchyItemBase](API\Plugins\NiagaraEditor\ViewModels\HierarchyEditor\UNiagaraHierarchyItemBase) > NewItemClass )