Apply additive animation on specified bone/bones

Right, sorry about the off-topic, I thought it would be closely related when I replied.

Base animgraph:

Slot blending anim layer:

And I didn’t realize you could output the current frame/time with play montage nodes. the return value says it can be “montage length” or “duration”, I assumed both would output the total length of the montage in different ways.

I don’t think there’s anything wrong with splitting the animation, I suppose I just don’t know how to do it the way you suggested, should I duplicate the same anim montage, and assign one as upper slot and the other as lower?