I use P3dO Explorer Pro for nearly all my library usage. I very rarely use the Poser library palette at all.

P3dO enables me to load content from anywhere, without having to obey the Poser library structure. For example, if I'm looking for shoes for Victoria 4, I go to Z:PoserLibrariesFiguresFemaleVicki 4 - S4 - A4ClothingFootwear, which is part of my own custom folder hierarchy. ALL my V4 footwear is in there, and the MAT poses, foot poses and materials that correspond to them are in sub-folders off that. Easy. :)

As well as Figures, I also have top-level library folders for Objects (small props, vehicles, weapons, furniture etc.); Places (buildings and environments); and Utilitites (lights, cameras, and anything else).

Hair has its own folder structure and is treated differently, since it can often be fitted to other figures and my criteria for choosing it are different. I made a spreadsheet with all my hair items in it, categorised according to the figure(s) it fits, the style, and the technology (prop or conforming; transmapped, dynamic, or "plastic hat"). I'm also in the process of adding thumbnails to the spreadsheet, so I can sort by figure and style and see, for example, all the short transmapped hair which has a fit for M3.

I can heartily recommend P3dO, and Yarp isn't paying me to say this. (!)

The only problem I have is that the best-organised library in the world is no good if you can't remember that you even have a particular thing in the first place. But no Poser vendor has yet offered a solution for old age. (And why not?!? Come on, vendors, up your game!) :)

As for the stuff which may be interesting for future use, that's what wishlists are for...