Place the diced potatoes in a large pot and cover with water. Bring to a boil over medium-high heat and cook until tender, about 15-20 minutes. Drain and let cool.
In a large mixing bowl, combine mayonnaise, Dijon mustard, apple cider vinegar, garlic powder, onion powder, salt, and black pepper. Mix well until smooth.
Once the potatoes have cooled, add them to the bowl with the dressing. Gently fold to coat the potatoes evenly.
Add the chopped celery, red onion, sweet pickle relish, and hard-boiled eggs to the potato mixture. Stir gently until all ingredients are well combined.
If desired, sprinkle with fresh parsley for garnish. Cover and refrigerate for at least 1 hour before serving to allow the flavors to meld.