Using Clip Tool for Blender.
In the Pose skeleton I see many hidden bones like L-R breasts, belly, belly target slot, back torso target slot. Other than breast bones, those don't seem to do anything.

Also there are unhidden ones like export poles:

And many between feet including offsets and infos:

So I am wondering what all those are for.

The slots are hidden because they're not used for anything except IK targets, effects and other things from the game. The pole export bones are the poles for the elbows and knees for when you're using IK. The offset bones, are the offsets of the IK targets for the arms, legs and root. The info bones, are the influence of the IK targets, for example, L_info_1 would be an IK target with the number 0 index for the left arm. It's a complicated subject, and I myself am still trying to figure out to get the IK targets to work properly so this is all I can tell you for now

Thank you

Boobie bones? It's not that I prefer my boobies boneless, but what use could those have?

Idk where they used it in the game, maybe for the boob slider? But I would definitely use them for adding some jiggle physics in animations and allow them to move depending on the pose. Freedom to bubiez!

I'm pretty sure they're for the boob slider, it allows them to be scaled without adding an entire morph for just the boobs.