Edit Deformers > Blend Shape > Swap > 
- Specify Node
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If the base object shape you selected is influenced by only one blend shape deformer, you don’t need to set Specify Node on. If on, you can specify BlendShape Node and Existing Nodes. Default is off.
- BlendShape Node
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Specifies the name of the blend shape deformer whose target object shapes you want to swap. Only available if Specify Node is on.
- Existing Nodes
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Lists all the blend shape deformer nodes in the scene, and indicates the blend shape deformer whose target object shapes you want to swap. Only available if Specify Node is on.