You can cook the tater tots in an air fryer before adding them to the casserole. Pre-cooking the tater tots in the air fryer can help them become more crispy and browned before being baked in the casserole.  However, remember that the tater tots will continue to cook and brown as the casserole bakes, so you may want to reduce the cooking time in the air fryer to prevent the tater tots from becoming overcooked. It may also be necessary to slightly reduce the baking time of the casserole to compensate for pre-cooking the tater tots.