code: function(event) {
  
          event.preventDefault();
  
          if (window.kelmu.data[id].undoStackPointer < window.kelmu.data[id].undoStack.length - 1) {
  
            var sp = window.kelmu.data[id].undoStackPointer;
            if (window.kelmu.data[id].undoStack[sp + 1][0] !== window.kelmu.data[id].stepNumber) {
              originalRedo(event);
            }
  
            window.kelmu.data[id].undoStackPointer += 1;
            sp = window.kelmu.data[id].undoStackPointer;
            window.kelmu.data[id].stepNumber = window.kelmu.data[id].undoStack[sp][0];
            window.kelmu.data[id].subStepNumber = window.kelmu.data[id].undoStack[sp][1];
  
            createAnnotations();
            if (window.kelmu.data[id].actions.updateEditor) {
              window.kelmu.data[id].actions.updateEditor(true, true);
            }
  
          }
  
        }
docs: Functionality for redo button.