The Extra icon serves various functions in the Sidekick app.
If you are experiencing any issues with the app, such as Assigned Walklists not appearing, go to Extras and select "Reset App." You will then be logged out of the app, it will reset and you will then log back into the app. It is now officially reset.
If you do experience what you believe is a bug in the Sidekick app, hit Report Bug. You will then be prompted to type in the problems you are experiencing with the app and then hit Submit.