Well, the manual is a bit of a mess and would benefit from a complete re-write IMO. In this instance it seems to use 'content collection' to refer both to the stuff in your libraries and the 'favourites' feature that you can find described on Page 118 of the manual.

Note that the favourites feature doesn't organise your content, as such, it creates shortcuts to the actual library items. But it means that you can create 'collections' of stuff in ways that make sense to you.

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Windows 10 x64 Pro - Intel Xeon E5450 @ 3.00GHz (x2)

PoserPro 11 - Units: Metres

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