Stir together broth, scallions, garlic, leek, celery, salt, black pepper, and red pepper in a 4- to 6-quart slow cooker. Cover and cook on LOW until vegetables are tender, about 4 hours. Stir in beans, snap peas, spinach, and sweet peas. Cover and continue cooking on LOW until peas are tender, about 30 more minutes. Top with Parmesan cheese, and garnish with olive oil and dill. Serve immediately.