Bookmarks are a great way to highlight certain invoices for quick access later on. Rather than having to search for the invoice you need, you can instead add a bookmark which can then be accessed through the Booking > Bookmarks menu. This is great if you are working on a booking and need to make some updates later on once everything is confirmed.
To add a bookmark, pull up an invoice and look for a button in the left sidebar labeled Bookmark. Click on this button and you will see the bookmark icon change to a solid black. This now means the invoice is bookmarked and can be accessed through the bookmarks report screen.