If you look on the right hand side of the screen in the space below the latest post in a thread and above the text box, you will see two buttons- "Forum Suggestions & User Assistance" and "Top".

The first one tells you which forum you are in and if you click it, gives you a drop down menu that will allow you to scroll and navigate to any area that you have permission to use by clicking on the appropriate name, by-passing the need to go back to the main index page.

The second one that says "Top" does exactly that- takes you back to the top of the page you are on and then you can navigate from there.