Place the kielbasa between two chopsticks or skewers to avoid cutting all the way through, then slice into ¼-inch thick sections without cutting through completely.
Cut the sliced kielbasa crosswise into approximately 1-inch pieces, each containing about three rings, to yield around 40 bite-sized portions.
Combine Dijon mustard, apple cider vinegar, brown sugar, and Worcestershire sauce in a small bowl and split the mixture into two equal parts.
Add mayonnaise to one half to create a creamy dipping sauce, stir well, and refrigerate until serving.
Apply half of the plain mustard mixture over the kielbasa bites, making sure to reach between slices; reserve the remaining sauce for after cooking.
Arrange the prepared kielbasa bites in a single layer inside the air fryer basket, working in batches if necessary.
Cook the bites at 400°F for 7 to 9 minutes, shaking the basket halfway to promote even browning.
Once cooked, transfer bites to a serving platter and brush them with the remaining mustard sauce.
Optionally garnish with chopped parsley and serve these warm with the chilled mayo-based dipping sauce.
