I came up with a slow cooker recipe, and it came out well, so I'll write it down here.
1 sliced onion
2 sliced carrots
2-3 stalks celery, chopped
1/2 tbsp minced garlic
1/2 tsp each dried basil, oregano, rosemary, thyme
About 3 cups low sodium vegetable broth; added a little water
1 can tomato paste
1 chopped zucchini
A few handfuls of swiss chard
1 cup dried red kidney beans
About 1 cup dried Great Northern beans
1/3 cup soup shells
Saute the onion in olive oil until lightly browned. Combine the onions and everything else in the slow cooker (except for the soup shells, swiss chard and zucchini). Cook the soup shells in boiling water for 5 minutes. Set aside the soup shells, swiss chard and zucchini. Cook everything else in the slow cooker for 4-5 hours on low (or until beans are reasonably tender). Add soup shells, swiss chard and zucchini and cook for 20 minutes more.