Can not see the Redo icon beside the Undo icon on the notebook toolbar.
This is NOT a bug.
We have included this 'Redo' icon within the 'Undo' icon menu. You just have to double tap on the Undo icon to get the option to Redo. We had to do this to be able to include the new Audio icon on the toolbar without making it look cluttered and hence providing a clean UI.