Originally Posted by the sci guy

It's this, like at the top of a page.

Except its beneath the last post at the bottom of the page, and above the quick reply box. So when you reach the last post you just click the link that's right there to go back to the main forum list. It's an extra step to scroll all the way back to the top, and the forum nav drop menu on the bottom right is cumbersome.
This is especially useful when browsing the foums as a regular webpage on a mobile device and not using tapatalk or a mobile skin (both of which i hate).
We had it on the previous version of the board after I suggested it then too, but it got lost in the update.