Sidebar display of Installed Plugins??
What extension do you have that does that??

{Ctrl + Shft + A} opens the Add-ons Tab, select Plugins on the left side of that Tab.

I cannot open the Plugins no matter which way I try. If I click on the sidebar plugins icon I get the same results as clicking on Firefox/Add-ons. The sidebar opens and there is no list of plugins just a "Loading" in the middle of the sidebar which never completes loading. I am unable to see which addons are installed and working or get to any of their options.