Originally from this post.

I wrote a Thunderbird extension (and my first one too!) that allows the display of all available about: windows in Thunderbird. Shredder Alpha 3 and above is required though. It is called ViewAbout and can be downloaded from Mozilla Add-ons. (Firefox 3.0.x and above are supported from version 1.2, other applications are continuously added and [hopefully] supported.)

Enables access to various about: dialogs from the View menu. Every available and applicable about: dialog can be viewed, even those activated by other extensions.

about:, about:buildconfig, about:cache (and related), about:config, about:crashes, about:credits, about:license (generic Toolkit license), about:mozilla, about:neterror (seemingly useless), about:plugins, about:privatebrowsing, about:rights, about:robots, about:sessionrestore, about:weave.

These windows can be closed using Ctrl (or Cmd)-w. Note that some about: menu options may not show up in applications that do not support them.

Historical note: ViewAbout came about from a need to view about:crashes in Thunderbird, and it just expanded from there. ;-) 

I have also made ViewAbout’s AMO Dashboard public, so everyone can see just how many users need about:crashes or about:config and the like.

Development of ViewAbout has now shifted to Google Code GitHub.

Version changelog has moved.