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With this tool you create copies of your animation.
So you can save your animation(a clip), try something new you're unsure, and then switch between two or more versions of your animation to decide which you like. So you can save your animation passes, and if you messup something, you can get it back to a previous stage.
With this system, you can also work on two or more version of your animation in the same file
How It Works
When you create a new clip, it just duplicate the animation curves from the selected objects, then link it to a empty transform node. So, when you select your animation clip, it switch the duplicate animation curves with the original. When you replace or insert , it will copy the keyframess (in the specified range) from the duplicated anim curves to the original.