Drain mangos, reserving 1 cup syrup. Peel 3 strips of lemon rind with a vegetable peeler; juice lemon to measure 3 Tbsp. Combine reserved syrup, lemon rind, lemon juice, and crushed mint leaves in a small microwave-safe bowl. Cover and microwave at HIGH 2 minutes or until syrup begins to bubble. Cover and cool completely; chill.
Cut mango slices into cubes, and place in a large bowl; add kiwifruit, grapes, and pomegranate seeds. Remove lemon rind and mint from syrup with a slotted spoon. Pour syrup over fruit; toss. Cover and chill until ready to serve. Garnish, if desired.
Make Ahead: Prepare the syrup up to 1 day ahead, and refrigerate it until ready to assemble the salad.