So Inquisitor doesn’t show up in Safari 4’s toolbar or preferences, but it does work from the bookmarks view (Command-Option-B).
The menu only shows for a split second, so you have to use keyboard shortcuts. If you haven’t set any shortcuts for Inquisitor you can do so by editing your Safari preference file (~/Library/Preferences/com.apple.Safari.plist) and looking for keys starting with “kInquisitor”. Below is a partial view of my plist file for reference.
If you do not have the Property List Editor (part of Apple Developer Tools) you could try PlistEdit Pro (I have never used this) or just get down and dirty with the XML.
Remember not to use existing keyboard shortcuts to avoid conflicts.