I want my to change an animation with Layered Blend Per Bone?

Hello,

Got a character with a mixamo walk cycle animation. I want to have a version of the animation were they have a hand on their shoulder as though they’re carry something on their back. I have an idea of importing the character into blender and creating a 1 frame animation where the character has the hand on their shoulder, then using Layered Blend Per Bone to apply this one frame animation on top of the walk cycle when needed.

Is Layered Blend Per Bone the tool for this job? I think it lets me add my animation on top of another so say the right shoulder downwards so the walk continues as normal but my added shoulder holding animation is on top of it?

Actually now that I think on it. If I have the arm statically held in a 1 frame animation with the hand holding a shoulder strap, would the walk cycle and the movement of shoulder cause the hand to sway away from the body of that makes sense?