Doesn't seem like a very complex format to me at least.
There are short 4 byte strings throughout the file that mention:
DTRA, DSCA, DROT, TRAI, TRAD
The last two im not sure about(They might not even be tags for parts of the file) but the first 3 are definitely Translation, Scale and Rotation.
The bottom of the file has a list of all the bones the mesh associated with the animation has.
https://cdn.discordapp.com/attachments/419711036837330956/503170533517688832/chr_her_rabbidluigi_acting_chapterwin_intro_01.anim
Here's the file for Rabbid Luigi's chapter win animation in Mario + Rabbids.
And here is the model converted to FBX to apply the animation to.
https://cdn.discordapp.com/attachments/419711036837330956/503172364159156235/chr_her_rabbidluigi_tpose_01out.fbx
https://streamable.com/d5eum
In game example of the animation.
The format seems to be the same across every Snowdrop Engine game so there's that too i guess.