Spray the slow cooker generously with non-stick cooking spray so nothing sticks.
Arrange the chicken breasts in a single layer at the bottom of the crock pot.
Pour the marinara sauce over the chicken, then sprinkle in garlic powder, onion powder, Italian seasoning, paprika, and red chili flakes (if using).
Pour the chicken broth over everything so the chicken is mostly submerged.
Cover and cook on LOW for about 4 hours, until the chicken is fully cooked and tender.
Remove the chicken carefully and shred it with two forks, then return the shredded chicken to the sauce in the crock pot.
Add the cheese tortellini, shredded mozzarella, and heavy cream. Stir to combine and make sure the tortellini is mostly submerged in the sauce.
Cover and cook on LOW for another 30 minutes, until the tortellini is tender.
Stir in the baby spinach and cook an additional 10 minutes until wilted.
Sprinkle the grated Parmesan on top, taste, and adjust seasoning if needed. Serve hot.