uhm I may know an unofficial way to remove unwanted items from your library once you already put them on the map.... But I don't totally suggest this...
When you got your map setup and noticed that you added models your not wanting over there "for whatever reason we can call this part mass confussion"
Okay what you do to get rid of the unwanted models that you selected. Save your game then for me I just go ahead and close my FPSC all together
Next open your windows explorer and goto your FPSC directory
C:\Program Files\The Game Creators\FPS Creator\Files
Now depending on what it is you put in your library this is where we remove it ie your segment or entity folder now remember you can remove it or you can put the files somewhere else on your HD as a backup until we can replace it at a later time.
Then restart your FPSC load your map poof there gone those models you used to see wont be there...
Now I have done this several times on several maps and it has not degrade my mapping on FPSC at all...
But I only state that this has worked for me and I have not told anybody else about this so I can not guarantee this will work for you...
Have you downloaded your CLiPs today.