In place of the former Account tab that was at the bottom, there's a new "Search" tab that's designed to let you quickly and easily find articles in the Apple Support database.
With the removal of the Account tab, you can now access your account details by tapping your user icon on the main "Discover" screen. This section houses all of the information that used to be accessible via the separate Account tab.
Most users likely don't need super quick access to the Account options in the Support app, making the search change much more useful to those looking for help on Apple products.
The Apple Support app can be downloaded from the App Store for free. [Direct Link]