After finishing cave hermit it would be a nice touch to be able to have an interact menu with trolls, similar to after feeding an auroch a clover.
If the troll has mushrooms, "pick mushroom."
Third eye "peer into."
Probably some generic troll interaction for all trolls too.
Finishing the credo could also unlock a chest drumming emote, like the trolls do, "Troll greeting."
Edit: Could also function as quest givers maybe. Not sure what the H&H lore is on troll intelligence.