Add the mandarin oranges, pineapple, mini marshmallows, shredded coconut, and vanilla yogurt (or sour cream) to a large bowl.
Use a silicone spatula to gently fold all of the ingredients together until they are well distributed and coated with the yogurt (or sour cream).
Serve immediately, or wrap the bowl tightly and chill until ready to serve.
Garnish with marashino cherries, if desired.
Notes
Advance prep: 5 cup salad can be made up to 24 hours in advance, but some liquid may collect in the bowl. Just stir everything together before serving. Storing: Leftover salad can be stored in an airtight container or tightly wrapped bowl for up to 3 days in the refrigerator. Does not freeze well.