Begin by boiling a large pot of salted water. Add the elbow macaroni and cook for 7 to 9 minutes until al dente, then drain and rinse under cold water. Set aside to cool.

While the macaroni cools, finely chop the celery, onion, and red bell pepper. If using hard-boiled eggs, chop them too and keep everything in separate bowls.

In a large mixing bowl, whisk together mayonnaise, yellow mustard, sugar, white vinegar, salt, and pepper until smooth. Adjust if necessary.

Add the cooled macaroni to the bowl with the dressing. Fold in the chopped vegetables and sweet pickle relish, ensuring everything is coated.

Cover the bowl and refrigerate for at least 2 hours, preferably overnight, to allow flavors to meld together.