In a 4- to 6-quart slow cooker, combine the coconut aminos/Tamari sauce, natural sweetener, vinegar, garlic, ginger, and red pepper. Add the short ribs, arranging in a single layer. Lay the cabbage on top.
Cook, covered, on low for 7 to 8 hours until the meat is tender and easily pulls away from the bone.
Transfer the cabbage and short ribs to plates. With a large spoon or ladle, skim the fat from the cooking liquid and discard, but keep the cooking liquid in the slow cooker. Turn the slow cooker to high.
In a small bowl, whisk together the guar gum with 1 tablespoon of water until smooth. Whisk into the cooking liquid and cook until thickened, 2 to 3 minutes. Stir in the sesame oil. Spoon the sauce over the short ribs and cabbage and sprinkle with the scallions.