Here is a conclusive list of all the keyboard shortcuts to use while editing designs:
Selecting multiple items: hold down Shift while clicking items to select them.
Group items together: Ctrl + G for PC or Command-G for Mac.
Copy items: Ctrl + C for PC or Command-C for Mac.
Paste items: Ctrl + V for PC or Command-V for Mac.
Editing charts: click it and press Enter.
Exiting charts: press Esc.
Layering designs: use Command, Alt, and the up or down arrows on Mac, or Ctrl, Alt, and the up or down arrows on PC.
Undo action: Ctrl + Z for PC or Command-Z for Mac.
Redo action: Ctrl + Y for PC or Command-Y for Mac.
Nudge items: use arrow keys.
Delete items: delete key.
Bold: Ctrl + B for PC, Command-B for Mac.
Italic: Ctrl + I for PC, Command-I for Mac.
Underline: Ctrl + U for PC, Command-U for Mac.