custom prop

[yves COPPE]

Hello,


When I click "custom" in the tab-window properties of an object,
you have two fields :

custom property sets
or
property set keys


If I want to create one, in which window do I need to click the "New" button ?

And more generally, what's the difference between the two kinds of 
custom properties ?

I have read the chapter in the documentation but I don't understand the trick.


Thanks.
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