Creates a new, empty UV set on the current object. You can then create the UVs in the set using one of the mapping/projection methods. This feature is also available for use from the Polygons menu in the UV Texture Editor.
Create UVs > Create Empty UV Set > 
- Create UV Set name
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Type a name for the new UV set in the text field.
- UV Set Sharing
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You can choose to share this UV set (every instance has the UV set), Per Instance Shared (all selected instances share the new UV set), or Per Instance Unshared (all selected instances get a unique UV set).