In a large mixing bowl, combine the drained pineapple chunks, mandarin oranges, halved grapes, and miniature marshmallows.
In a separate medium bowl, whisk together the sour cream, heavy whipping cream, and powdered sugar until smooth and well blended.
Pour the cream mixture over the fruit and marshmallows, then gently fold until everything is evenly coated.
Add the shredded coconut and chopped nuts, folding gently to distribute throughout the salad.
Cover the bowl with plastic wrap and refrigerate for at least 2 hours or overnight to allow flavors to meld.
Just before serving, give the salad a gentle stir and top with the halved maraschino cherries for a beautiful presentation.