Although there is currently not a specific feature for Credit Notes, you can create them by adding a negative dollar amount Menu Item to an Invoice:
In the Booking Summary, click the Invoices tab
Click New Invoice
Click Add Item
You can then add a new item (you can name the item "Credit Note") and enter a negative dollar amount.
For accurate reporting, it’s recommended to create a dedicated Revenue Category for credits. This ensures that credits are properly categorized and reflected in your financial reports.