In a large mixing bowl, beat the softened cream cheese with an electric mixer until smooth.
Gradually add the powdered sugar and vanilla extract, mixing until well combined and creamy.
Gently fold in the whipped topping until the mixture is light and fluffy.
In a separate bowl, combine the strawberries, blueberries, pineapple, and mini marshmallows.
Pour the cream cheese mixture over the fruit and gently fold until all the fruit is coated.
If desired, fold in the chopped nuts for added crunch.
Cover the bowl with plastic wrap and chill in the refrigerator for at least 1 hour before serving.