Pulse the cranberries in a food processor until finely chopped without becoming a puree. Toss with sugar and let stand for 10 minutes.
Dissolve the gelatin mix completely in the boiling water in a heatproof bowl, stirring for 2 minutes. Stir in cold water.
Refrigerate for 35 to 50 minutes, additional to active prep time, until the gelatin thickens to the consistency of unbeaten egg white but has not set.
Fold in the cranberries with their juices, drained pineapple, apple, celery and walnuts. Spoon into a 2-quart serving dish.
Cover and refrigerate for at least 4 hours until fully set. Serve cold in spoonfuls, keeping the dish chilled until the meal.