Poser itself doesn't have a search feature. If you know the name of the content item, you can use the search function of Windows to locate the correct folder - it'll have the same name in the Poser library.

60 GB? That's big. I can recommend organizing the content into multiple runtimes - makes starting up Poser a lot faster.
Quite a hassle thougn, you'd have to figure out what geometry and texture folders to move. 
Subfolders within the libraries can also help keep things organized. The main advantage is not having to move geometry/texture folders, and you can move library folders at will (within the content type folder, it's not possible to move a .pz2 pose file to a subfolder of the character library...)

The pen is mightier than the sword. But if you literally want to have some impact, use a typewriter

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