Cut chicken into 3/4-inch pieces. In a 4-quart slow cooker, combine chicken, celery, onion, undrained tomatoes, broth, tomato paste, Cajun seasoning, garlic, and salt. Cover and cook on low-heat setting for 4–1/2 to 5–1/2 hours or on high-heat setting for 2–1/4 to 2–3/4 hours. If using low-heat setting, turn to high-heat setting. Stir in uncooked rice and sweet pepper. Cover and cook about 30 minutes more or until most of the liquid is absorbed and rice is tender. Before serving, thaw shrimp, if frozen. Stir shrimp and parsley into chicken mixture.