Heat dressing in large skillet over medium-high heat. Add mushrooms and kale; cook, stirring constantly, 5 min. or until mushrooms are tender. Drain.
Mix egg, Neufchatel and ricotta in medium bowl until blended. Add dry seasonings, and 1/4 cup each mozzarella and Parmesan; mix well. Stir in mushroom mixture. Spoon into resealable plastic bag.
Cut large piece off one bottom corner of bag; squeeze Neufchatel mixture into both ends of each manicotti shell.
Spread 1/2 cup pasta sauce onto bottom of 6-qt. slow cooker sprayed with cooking spray; cover with 7 manicotti. Top with 1/2 cup of the remaining pasta sauce and 1/4 cup of the remaining mozzarella. Cover with layers of remaining manicotti, pasta sauce, mozzarella and Parmesan, then cover with lid.
Cook on LOW 4 to 6 hrs. (or on HIGH 2 to 3 hrs.).