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This file can be named and saved wherever you choose among your installation. You just have to Assuming you saved the file in "~/MyCollective.json", you just add the following line in the 3delight.config configuration file so that 3Delight knows about it:
collective ~/projects/MyCollective.json
With this information, the 3Delight Collective option will be available among the Processing Options and accompanied with a menu to select which collective to use (if there are more than one):
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