Pat wings dry. Toss with salt, pepper, garlic powder, onion powder, and smoked paprika.
Whisk barbecue sauce, honey, apple cider vinegar, Worcestershire, and hot sauce in a bowl.
Layer wings in the slow cooker. Pour sauce over and stir to coat evenly.
Cover and cook on High for 3 hours or on Low for 6 hours, until very tender.
Stir cornstarch with water to make a slurry. Mix into the cooker and cook 10–15 minutes until glossy.
Stir in butter. For crisp edges, broil wings 2–3 minutes per side, then toss with thickened sauce.
Serve hot with extra sauce and a sprinkle of parsley.