I am curious. You say it didn't work for you...Do you mean that like myself, you were unable to enter in new values after going to about:config in the address bar of microb?

Or that you found a way to add values from that place, and despite that, you were unsuccessful?

If you havent been able to add values, try antezz's recomendation which worked for me, either by using winSCP, navigating to prefs.js, and editing on your pc, or using an editor like leafpad, like he just mentioned.