I found this interesting page:
Maybe one of the things there will work for you. As a prerequisite, you have to go to
the page for VDH betas for Firefox & instead of just clicking the green button, pop up
the context menu on the button & execute Save Link As.
One of the steps there seems couched in somewhat outdated terminology. The page you want
is the one you get when you navigate the Firefox menus: Tools -> Settings, then pick the
Extensions section of Firefox settings. The cog they refer to appears on that page of