There is no attribute that allows a Copper Area to be defined as having Exposed Copper. It is not possible to copy and paste the shape of a Copper Area onto any layer other than a copper layer. It is not possible to convert a Copper Areainto something else that can then be copied and pasted onto another layer. It is possible however, to add apertures in the Solder Mask layer using the Solid Region Tool set to Solid, applied to the appropriate top or bottom Solder Mask layer.

Thanks a lot for your support.