You can move any word in a wordbook to a different wordbook.
To do this:
Open a wordbook, select the icon Organize wordbook (1) => Click to select words you want to move (2) => Click the Move icon (3)
On the page Select wordbook, tick the wordbook you want to move the selected words to (4) => Click Add (5)
The words you selected are now moved to the new wordbook!