Place a long, shallow dish and a medium mixing bowl in the freezer for 5 minutes until well-chilled.
In the chilled bowl, beat the heavy cream with the powdered sugar and vanilla extract to soft peaks, 2–3 minutes; keep refrigerated until assembly.
Arrange the split banana halves in the cold dish with cut sides facing inward, 30–60 seconds.
Scoop the vanilla, chocolate, and strawberry ice creams into three 0.5-cup mounds between the banana halves, placing vanilla in the center, 1–2 minutes, keeping the scoops firm.
Spoon pineapple topping over the vanilla scoop (about 2 tbsp), strawberry topping over the strawberry scoop (about 2 tbsp), and drizzle chocolate syrup over the chocolate scoop (about 2 tbsp), 1–2 minutes, until the sauces gently cascade down the sides.
Dollop or pipe the whipped cream into three swirls—one on each scoop—using all the whipped cream, 30–60 seconds, until the swirls hold soft peaks.
Sprinkle the chopped peanuts evenly over the sundae, 10–15 seconds, then top each whipped cream swirl with a maraschino cherry and serve immediately.