Clicking on "Add engines..." from the search bar takes you to a site which should try to install search bar plugins. However, it doesn't work unless you are root.
Steps to Reproduce:
1. Go to http://mycroft.mozdev.org/quick/dictionary.html
2. Click on one to install (e.g. Dictionary)
3. Click OK.
Plugin should be installed.
Doing the same process as root works. This is because
/usr/lib/MozillaFirebird/searchplugins is only writeable by root. Ideally this
would be overridable in ~/.phoenix but I don't think you can (I've tried
creating a ~/.phoenix/searchplugins directory and adding stuff to it, but it's
Easy workaround is using sudo to start up as root, then quitting immediately
after installing. But running a web browser as root scares the bejeezus out of me.
Can't help you with this one. Many of the extensions have been fixed to install optionally into the user profile. Hopefully more of them will follow this trend. Not something we're going to fix at the distribution level. Sorry!