Heat 2-3 cups of water in a pot over medium heat. Once the water comes to a boil, add the potato cubes and 1 tablespoon salt to the pot and stir well.
Cover the pot with a lid and reduce the heat to low. Cook covered for 10 minutes or until the potatoes are fork-tender.
Drain the water and run the cooked potatoes under cold water to stop the cooking process and cool them down.
Stir together mayonnaise , yellow mustard sauce, granulated sugar, apple cider vinegar, salt, cracked black pepper, celery seeds (optional).
Stir together in small mixing bowl.
Add the cooked and cooled potatoes to a large mixing bowl. Add chopped egg, celery ribs, red onions, and sweet pickle relish to the bowl. Pour the dressing over the salad and toss everything well.
Check for seasonings and add more if needed. Chill the salad in the refrigerator for a few hours before serving.