Are the props parented to one prop, or a number parented together?  You might be able to load them into the library together using Select Subset.  I find when saving multiple props into one library item they tend to loose the connection to what they are parented to - at least in Poser 7 (and earlier versions I think).

Sometimes I save a figure pose and save the grouped items into a subset.  When I want to use the items I dot the figure's pose, load the saved pose, load the items and do the parenting, and then restore the original scene pose using the saved dot ... Does that make sense?

There are various work arounds to whatever limits I find in Poser.  If you don't need all of the various pieces to be separate props, why not combine them into a single prop item?  Either that or make a figure prop with moving parts ...

I guess that's all I can suggest for now.  Best Wishes, Rªnce