Cook the elbow macaroni according to package instructions until al dente. Drain and rinse under cold water to cool. Set aside.
In a large bowl, whisk together the mayonnaise, apple cider vinegar, Dijon mustard, sugar, salt, and black pepper until smooth.
Add the cooled macaroni, celery, red bell pepper, red onion, peas, and chopped hard-boiled eggs to the bowl. Gently fold everything together until well combined.
If using, stir in the chopped parsley for added freshness.
Cover the salad and refrigerate for at least 1 hour to allow the flavors to meld. For best results, chill for 2-3 hours.
Before serving, give the salad a gentle stir and adjust seasoning if needed.