code: public void showViewAndWait(Modality modality) {
          if (isPrimaryStageView) {
              showView(modality); // this modality will be ignored anyway
              return;
          }
          if (stage == null || currentStageModality != modality) {
              stage = createStage(modality);
          }
          stage.showAndWait();
      }
docs: Shows the FxmlView instance on a top level {@link Window} and waits to be closed before
  returning to the caller.
  
  @param modality
  See {@code javafx.stage.Modality}.