urrggh, it has been too long. When I was modding fallout years ago I remember we could paste a new animation over an unused animation group slot

ie use uppercut animation (sneakH2HAttackRightHand.hkx) at Attack7 in the H2H set of animations. Attack 7 not being used, this would cause no problems

But I cant remember what to rename sneakH2HAttackRightHand.hkx to, or where in the folder structure to put it. My BSA crawling and google-fu have been useless so far

If Saiden or TalkieToaster are around I know they have the answer, but help from anyone would be appreciated

Animations are no longer slotted you can no longer just drag and drop anything into an unused slot.

The game uses Behavior which is far more freeing (For Bethesda) and far far far more restrictive for modders, there is a thread around hkxcmd that has a good amount of information about Behavior the very small amount we actually know atm.