Melt marshmallows with 1/4 cup heavy cream in the top of a double boiler over simmering water, stirring frequently until smooth, about 5 to 7 minutes. Set aside to cool completely.
Beat remaining 1 3/4 cups heavy cream in a glass or metal bowl until foamy. Gradually add confectioners' sugar, continuing to beat until soft peaks form. Lift your beater or whisk straight up: the cream will form soft mounds. Gently fold pineapple, coconut, vanilla extract, and cooled marshmallow into whipped cream.
Layer about half the pound cake cubes in a trifle bowl. Spread about half the whipped cream over the pound cake and scatter about half the quartered mango chunks over the cream. Sprinkle about half the macadamia nuts over the mangoes. Repeat layers. Chill for 2 to 3 hours before serving.