code: function makeDraggable(context, element, addMarker) {
  
      previewSupport.addDragger(element, context.dragGroup);
  
      if (addMarker) {
        canvas.addMarker(element, MARKER_DRAGGING);
      }
  
      if (context.allDraggedElements) {
        context.allDraggedElements.push(element);
      } else {
        context.allDraggedElements = [ element ];
      }
    }
docs: Make an element draggable.
  
  @param {Object} context
  @param {djs.model.Base} element
  @param {Boolean} addMarker