A few questions about your design here.
BPMasterWeapon, this is the actor blueprint that is the weapon.
So you seem to want to separate the two objects in that blueprint?
You have the sheath and the sword in the same blueprint, attached to the same scene root.
You don’t want that, you need two separate objects.Or management between them will have to be done using local space, to me that seems like a painful approach.
As separate objects you are able to attach one to the other and detach and move attachment to your character mesh as you see fit without penalty.
Also, I would convert these to static mesh unless they have some bone I would use.
I would inquire about your box, is this for collision? do you intend to make it collidable? or perhaps you intend to use that box for a box ray.
What I do is simply place some socket’s on the mesh which I use in world space during animations to generate ray’s to test for collision.
Edit:
Another option I suppose if you insisted on a single blueprint for both objects, would be to detach one of the mesh components, still this seems a bit too much extra work.