If you right-click on the page, "Back" is usually the first item. It's a lot quicker to get to than the Back button, even if it were clickable from the left edge of the screen.

Long ago I removed all the navigation buttons from my Firefox toolbar; I much prefer having room for larger URL and search bars.

I'm actively working on this issue. Feel free to add yourself to the CC list so you can be notified of any changes.