I was hoping to detect whether ctrlKey was pressed from the event object passed to the onSelect event, but I can't find it anywhere.
Is it being stripped on purpose or is it hiding somewhere?

Hello Peter,

The ctrlKey property is not passed to the select event of the PanelBar, but only the currentTarget property of the event argument of the click. This is why you are not able to see the ctrlKey property available. As such functionality is not available built-in, you can modify the source code in order to extract the required property.

Regards,
Kiril Nikolov
Telerik