Coat the insert of a 4-quart slow cooker with cooking spray.
Stir artichoke hearts, cream cheese, green chiles, yogurt, jalapenos, mayonnaise, salt, pepper, and onion powder in a medium bowl until combined. Pour into the sprayed insert. Cover and cook on high for 2 hours. Add the mozzarella and stir to combine. Transfer to a serving dish and garnish with red onion and parsley, if desired.