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There's a tiny little feature called Show in Collection that Adobe added to the contextual menu that appears when you right-click a photo just about anywhere in Lightroom.
It allows you to see what collections that photo has been added to and it allows you to jump over to viewing any one of the collections shown.
Give it a try the next time you want to see how many collections a given photo is included in or when you want to jump to another collection you know that photo happens to be a member of. Note that smart collections are not included in the listing.