Pour 1 cup cranberry juice in a small saucepan; bring to a boil. Add Jello, stirring until dissolved. Stir in remaining cranberry juice and salt. Refrigerate to chill just until slightly thickened. Fold in apple, celery, and nuts; pour into a 4-cup mold. Chill until firm. Unmold cranberry salad onto a serving plate. Serve with whipped topping. Cranberry salad mold serves 6 to 8.