Ok... that's easy. Go to the place in the forum that you'd like to have a quick icon for (i.e. click on WATCHED THREADS if you have them setup or you can navigate to whatever portion of the forums you like). Once you're there, highlight the address in your bar. right click the highlighted address and click COPY. Then right click the space underneath of your address bar and click PASTE or NEW BOOKMARK. If you use the new bookmark option then paste your URL into the LOCATION line. You can name it whatever you like and it should take on the SB icon by itself. Whoala. New quickie.
You can delete the old one that you say doesn't work anymore because that specific address doesn't exist anymore.