A curtain wall panel may need an opening in it, such as a vent. You can create an opening by editing the panel as an in-place element.
Model panel
Edit In-Place.
for the panel. The pin icon indicates that the panel properties are determined by the curtain wall system. When you click the pin, you can override properties for the selected panel. The selected panel is the only geometry available for editing.
Mode panel
Edit Extrusion. For example, you could add a door-like opening to the panel.