Drain the pineapple chunks thoroughly in a fine-mesh strainer, pressing gently to remove excess liquid—this prevents the salad from becoming watery. Drain the mandarin oranges as well, reserving any liquid. Pat the maraschino cherries dry with paper towels to remove excess syrup. Slice the bananas into 1/2-inch rounds and immediately toss them with the fresh lemon juice and sea salt in a small bowl; this prevents browning and seasons them gently.

In a large mixing bowl, add the peach pie filling first, then gently fold in the drained pineapple chunks and mandarin oranges. Add the halved red grapes, mini marshmallows, and patted-dry maraschino cherries. Finally, fold in the lemon juice-dressed banana slices using a rubber spatula with gentle motions to avoid crushing the soft fruits and marshmallows. I like to mix this just until everything is evenly distributed—overmixing can break down the delicate fruits.

Transfer the fruit salad to a serving bowl or individual serving dishes. Cover with plastic wrap or a lid and refrigerate for at least 2 hours before serving. The chilling time allows the flavors to meld and the marshmallows to soften slightly from the fruit juices. Give it a gentle stir just before serving to redistribute any settled juices throughout the salad.