When you're working with pose shapes for pose space deformations, you may need to duplicate a pose shape so that you can edit and update it separately from the base mesh. This is especially important if you want to bring the shapes into other applications, such as Autodesk Mudbox, for sculpting and fine-tuning. When you're done working on that duplicated pose shape, you can update the original pose shape with it.
To duplicate pose shapes
The pose shapes are duplicated and placed directly below the original pose shapes using its name plus a "_Copy" suffix. You can rename each duplicate as you like.
To update pose shapes
The pose shape is updated with the selected mesh's shape.