As with the main Planning section, you can also review the history for the product backlog. As an example, this can be important when looking at which items have been added or deleted, or when comparing current requirements with those at the starting phase of the project.
You access the backlog history in the More.. menu and then View product backlog history. The keyboard shortcut is Ctrl + J, or Cmd + J.
If there is a difference between the historic version and the current, it is marked in grey, as seen below: