Pass "Windows key" to unattendant Client

Pass "Windows key" to unattendant Client

Hello 

We like to use Zoho Assist to manage remote "Digital Signage Clients". 
On this Clients the only way to go out of the full-Screen Application is to hit the "Windows Key" on the Keyboard.

How can I pass the Window Key to the remote Client..? Is there any Shortcut..?

Regards Beat