Drain the crushed pineapple and pineapple tidbits over a bowl, pressing lightly to squeeze out the juice (reserve the juice).
Combine the sugar, flour and 3/4 teaspoon salt in a medium saucepan. Whisk in the reserved pineapple juice and the eggs. Bring to a simmer over medium heat, stirring constantly, and simmer until thickened, about 2 minutes. Strain the custard into a large bowl, cover with plastic wrap and refrigerate until just cool.
Meanwhile, cook the pasta according to package directions. Drain and run under cold water to stop the cooking.
Reserve a few slices of mandarin orange for garnish and set aside. Add the cooked pasta, pineapple, the remaining mandarin oranges, coconut and marshmallows to the custard and stir to coat. Add the whipped topping and stir until well mixed. Transfer to a serving bowl and top with the reserved mandarin slices and the pinch of coconut. Cover with plastic wrap and refrigerate at least 2 hours and up to overnight.
Copyright 2018 Television Food Network, G.P. All rights reserved.