Across the top of the library, there is a row of icons which designate different categories of Poser content.  By default, when Poser is opened the library will appear in the Character category, denoted by the Figure in the icon on the left end button.  Selecting the icon to the right of that will place you in the Pose Category; to the right of that is the Expressions Category, etc.  And each icon has a different image based on it's content.  This is the way to navigate through the Library based solely on content alone.  If you have organized your external runtimes according to content type, you will need to switch to that particular runtime folder to locate the content.