Dissolve strawberry Jello in 1 c boiling water. Add 1 c cold water. Refrigerate in a shallow dish for 1 hour until slightly thickened. Toss banana slices with 1/4 c of the pineapple juice from the can. Set aside. Chop pineapple chunks if desired.
While the Jello is setting up, start your trifle layers. Place half of the cake cubes in the bottom of a trifle dish. Put half of the mashed strawberries and sliced strawberries on top. Add half of the bananas and half of the pineapple pieces next. Spoon half of the prepared Jello on top. Refrigerate trifle for 20-30 minutes.
In a small bowl, whisk the pudding mix with the milk for 2 minutes. Let sit for 2 minutes to thicken. Spread half of the pudding on the trifle. Repeat all layers - cake, strawberries (mashed and sliced), bananas, pineapple, Jello, and pudding. Top with Cool Whip. Serve immediately or refrigerate until serving. *Optionally, you may add 1/4 c toasted slivered almonds to the top when serving.