If a plugin is disabled then you get a message asking to enable that plugin that brings you to the Tools > Add-ons > Plugins window. If you want to use that plugin then you can click the Enabled button, no restart needed.
You can force a rescan and enable all plugins if you delete the file pluginreg.dat in the Firefox Profile Folder.
Help > Troubleshooting Information > Profile Directory: Open Containing Folder
Unfortunately all these answers are dealing with the shaded plug in's, I am looking for the answer to his other question.... WHICH plug in's should I have on my FF, what ones do I need to have installed?