In a 4-quart container, soak red beans in 12 cups water; leave uncovered overnight. After soaking, discard soaking water, and rinse beans with fresh water. Set aside.
In a large skillet, heat oil over medium-high heat. Add sausage, and cook until browned, 8 to 10 minutes. Remove sausage from pan, and set aside. Deglaze skillet with 2 tablespoons chicken broth, add onion, and cook until softened and beginning to brown, 7 to 9 minutes. Add celery and bell peppers to skillet, and cook until soft, 3 to 4 minutes.
Transfer mixture to a 4-quart slow cooker. Add garlic, remaining broth, tasso, brown sugar, bay leaves, salt, hot sauce, black pepper, Cajun seasoning, sage, chipotle pepper, cayenne pepper, reserved beans, and cooked sausage, stirring to combine.
Cover, and cook on high until beans are softened and cooked through, 3 to 4 hours.
Add chopped parsley and green onion to red bean mixture. Serve over rice. Garnish with additional parsley, if desired.
Recipe by Louisiana Cookin' at https://louisianacookin.com/slow-cooker-red-beans-rice/