SnapShot is used in Story Telling View.
In the above Image I took snapshots from my dashboard and created a new story.
I can write descriptions to it and explain it (can be useful for end users) just like book marks but users can write their own views.
On the right side you'll see a camera Icon, from there you can export your snapshots into story.
Not an answer to your question, I do not know where they get saved. But just know the use of it.
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