Don't be tempted to stir! By keeping the ingredients in layers, you can serve the brats in buns, top them with the onions, and then serve the beans as a side dish.
Vegetarian brats vary by brand, but generally, most require very short cooking times and will dry out or fall apart if overcooked. The slow cooker offers a great, gentle slow heat, but this recipe requires just 3 to 4 hours and is not one that can cook all day. Do not overcook the dish. You might want to try different brands of brats so you can find the brand you prefer to use.