The mousewheel zooms in & out when it is placed in the timeline ruler, just below the navigator.
If you want the horizonal scrollbar back do the following :
Make sure you have the ‘Mixer’ button highlighted, above the transport.
In the ‘View’ menu, select ‘Customize Editor Profile ‘
In the list that appears, underneath ‘Tracks’, select ‘Space (Recess)’
Click ‘Insert New’ and then pick ‘scrollbar’ from the popup menu.
This will add the scrollbar into the Mixer view.
To add it to the Editor & Tracks view, just make sure either button is highlighted (above the transport) before you select ‘ Customize Editor Profile’.