Ok I'm going to wander off topic here for a minute.
Would [PET_EXOTIC] work as well as [PET] for allowing Goblins to bring Beak Dogs when on the attack? Would this also be why they don't bring trolls?
Well, the answer to the question Kamudo was asking was different from the reason why goblins don't ride Beak Dogs. Goblins don't have the [COMMON_DOMESTIC_MOUNT] token, so they don't use mounts at all. I'm about 60% certain that Beak Dogs would need [PET], too, or [PET_EXOTIC] if goblins had [USE_ANY_PET_RACE].
The problem is that I don't think that you can limit them from coming mounted on horses, too, without shenanigans involving the [GOOD] token and adding [USE_GOOD_ANIMALS] to anyone you want to use horses.
As to why they don't bring trolls, I have no idea. My idea as to why they don't ride beak dogs is, as mentioned, the fact that they ride nothing due to lacking [COMMON_DOMESTIC_MOUNT], but I don't know of any tag that would make a civ bring another non-mount race, so that doesn't explain the lack of trolls.
If I delete the Data/Object files, will they replace themselves with the updated Raws when I load up the game up? Or, how does that work?
Yeah, every file in the data/objects file is game-usable versions of the raw/objects folder. Clearing it when you mod prevents duplicate entries and some other things, which can cause Bad Stuff to happen, but is totally painless.
Edit: Well, I edited the raws n stuff successfully. But I can't embark with Beakdogs. At least I have other animals available now though. So, I'm just gonna play for a bit and see how things work.
It's possible that your civ simply isn't in a location where it has access to beak dogs. They spawn only in marshes, and goblins normally spawn only in mountains, so you're actually fairly unlikely to see them without changing their biome tokens.