Here is a conclusive list of all the keyboard shortcuts to use while editing designs:
Hold down Shift while clicking items to select all of them at once:
To group items together, hold down Ctrl + G for PC or Command-G for Mac.
To copy items, hold down Ctrl + C for PC and Command-C for Mac.
To edit a chart, click it once and press Enter.
To exit edit mode on a chart, press Esc.
When layering designs, use Command, Alt, and the up or down arrows on Mac, or Ctrl, Alt, and the up or down arrows on PC: