It seems Javascript does not really like running in sidebar as any page I tried have JS not working. Also cookies are not preserved which makes pages asking for l/p on each click. Also FF sidebar which this plugin uses has pretty narrow max width. This can luckily be "fixed" and make it resize without limits by installing https://github.com/Aris-t2/CustomCSSforFx and enable "./css/generalui/sidebar_width_unrestricted.css" (search for "sidebar" in "userChrome.css" and uncomment). Tested with FF 73.