For an active selection of curtain wall, the Modification > Modify Selected tab lists modification tools in the tool groups provided for curtain wall manipulation:

You have many modification options. You may choose to modify an entire curtain wall element by selecting Modify > Modify Properties, or you may choose modify individual elements within the curtain wall by selecting Modify > Modify-Sub Elements. In both cases, the modifications are done with a traditional "modify instance" dialog.

Also, based on the currently selected element of the curtain wall, there are other manipulation tools available in the Modify Curtain Wall tool group. For instance, if a mullion on the top edge is active, the Toggle Entity Line tool turns the entire line of the mullions invisible. Other tools here affect the entire curtain wall, and are independent of which sub-element. For instance, the Flip Curtain Wall tool mirrors the curtain wall face orientation.

Alternatively, tools appearing here can also be accessed on curtain wall elements via edit handles and mini toolbars. The grip handles available in the mini toolbars for curtain wall elements are capable of performing above modifications as well as additional basic manipulations, that include Move, Copy, etc.