Reuse Blendshapes: You can use blendshapes from another asset as a starting point for your new blendshapes set.

Source defines the group of the source correction shapes. This is usually referenced. You can use the Blendshapes step from the Assembly tab of the Builder to load the reference asset. Make sure to match the prefix.

Update Blendshapes: If topology or shape changes have been done on the model and the rig was rebuilt accordingly, you can update all blendshapes to transform to these changes. Note that the result won't be perfect. Some manual adjustments and smoothing might be needed in certain areas, depending on the scale of change that was done.