Here is a list of plants you can use in long cooked meals like soups, curries, casseroles & stews.
To my mind, there’s twice you can use them in this type of meal. Early on you’ll want to be adding root and stem vegetables, but also some leaves to improve both the flavour & nutrients of the stock.
Just prior to serving, you could add some more leaves for flavour & texture. Normally you’d just want them wilted – not cooked.
Play around with it to find the way you like it, but when you consider how nutrient rich these plants are, it makes sense to add as many as you can to these types of meals.