code: protected void showCustomSlideStep(final Node node) {
  
          addSubSlide(node);
          final Node nextSlide = this.subSlides.get(model().getStepPosition());
  
          if (this.currentSubSlide == null || nextSlide == null) {
              // No Animation
              this.currentSubSlide = nextSlide;
          } else {
              performStepAnimation(nextSlide);
          }
      }
docs: Show a programmatic built node as a sub slide.
  
  @param node the node built programmatically