Can i add anything to a dough that has already done 2 rises?

It would be easy to add seeds/stuff to the outside.  Paint the dough with a little water, or milk, or egg wash (egg white with a little water) to get things to stick. Maybe sesame seeds, flax seeds, chia seeds, sunflower seeds, caraway, poppy seeds, fennel, coriander.

Another trick to enhance flavor is to wait 18 to 24 hours before cutting open the baked loaf, especially if you used sourdough.

It’s a little hard to evenly distribute things into the dough after bulk fermentation is done but then again, it also depends on the type of dough you’re making. It’s a lean dough, I’d only incorporate nuts/seeds/fruits/etc. into the dough before letting it rise but for soft, enriched doughs, you could probably get away with kneading or folding things into them before shaping (still, if you’re going to be adding seeds or fruits, I’d say it’s still preferable to add them before letting the dough rise). But you can absolutely add a whole variety of seeds or grains to the top of your shaped loaf. It can be done either before or after and the final proof and you just use water or an egg wash to coat the loaf before hand and then sprinkle on whatever toppings you want. If you want the entire top to be coated in seeds, then before the final proof, you can take the wetted loaf and roll it around a tray of seeds to get full coverage.

But if you’re finding the bread itself to be bland, then you might want to look for a different recipe or change your approach to the recipe. Remember, the more you can slow down the fermentation of dough, the better the final loaf is going to taste. The best way to do this is to either throw the dough in the fridge to cold rise for 12-72 hours, or to use a preferment like a poolish, biga, pate fermentee, or sourdough starter (there are guides online which show you how to convert any dough recipe into one with a preferment).