All Poser versions have limitations on how to extensively manipulate the library.  P8 and PP2010 give you better control and ease to arrange your library as you want.  However, the ability to rearrange folders and content within the program still falls short.  Your best alternative is still using Windows Browser or ShaderWorks' P8 Extended Library which should work just as well but within Poser.  That application can be found @ RuntimeDNA.