Keeping a business running smoothly depends a lot on communication, so I can see how having the ability to leave notes for other departments would be useful. There currently isn't an integrated feature for leaving notes for other users, but you may be able to make use of the memo section on transactions as a workaround. That way, you can leave any necessary details that another department may need.
Reports also have a comments feature that you can make use of. Simply follow these steps.
Learn more about reports in QuickBooks Desktop by reading the Understand Reports article.
I hope that helps! Let me know if you have more questions.