Mix red cabbage and sauerkraut and let it sit in the fridge overnight. The cabbage will soak up the fermented liquid in the sauerkraut and soften.
Place edamame in a heat safe bowl. Bring 2 cups of water to a boil in a kettle and pour over edamame. Place a plate or lid on top of the bowl and let them sit for 5 minutes. Drain the hot water and rinse under cold water until they are no longer emitting heat.
Place edamame, garlic, lime juice, vegan mayonnaise, cilantro, mint, dill, ground mustard, sea salt, and ground black pepper into a food processor. Process until it's well combined but still has some texture to it. Refrigerate until ready to assemble sandwiches.
To assemble the sandwiches, spread vegan mayonnaise onto one side of each slice of bread. Then add edamame mash to one side, top with the cabbage/sauerkraut mixture, tomato slices, baby spinach leaves, and top with another slice of bread.