boomarklet has own css definition in bookmarklet.css - we introduced configuration parameter which says where bookmarklet sources (js and css... in future even other sources) resides - which too solve problem when we want to customize from where bookmarklet and its sources are loaded from - like on staging environment we want to serve bookmarklet sources from current devel branch and not from the master (until now it inject bookmarklet directly from from github using master branch link)
when authenticated as  admin you can see application configuration on /admin/settings