Baking soda adds more draw to the sauce (makes it more sliperry). If you do not want much slip, do not use the baking soda, especially if you used the food processor to chop the okra.
Also the eggplant is not necessary, its just another way to add more veggies to the stew. The dawa dawa is highly recommended but not essential. It gives a really nice flavour that is very difficult to describe