Bring a large pot of salted water to a boil. Add the elbow macaroni and cook according to package instructions until al dente. Drain and rinse under cold water.

In a mixing bowl, whisk together mayonnaise, Dijon mustard, apple cider vinegar, salt, and black pepper until smooth.

In a large bowl, combine the cooked pasta, chopped eggs, celery, red bell pepper, and dressing. Mix gently until everything is well coated.

Cover and refrigerate for at least 30 minutes to allow flavors to meld. Serve chilled, garnished with additional chives if desired.