How to define new property?

[vrapp]

In file associations I see how to assign profiles to file types, and in profile manager I can create new profile with a set of available properties. But how to create new property? In the documentation I saw property "Tags" that seems to be new; but how to define it?

I want to add property "Copies to Print", to tell how many copies of the given PDF file have to be printed in one particular process in our office.