Within a Windows Sandbox, if I press Ctrl+Alt+Del, it does not act on the Sandbox, even if I am in full-screen mode (this is on Windows 10). In fact, no system key combinations operate on the Sandbox and always go back to the Host system, so if I just press WinKey it will open the Host Start Menu and not that of the Windows Sandbox (again, even if the Sandbox is maximised in full-screen at the time).
Within a Remote Desktop session, we can of course press Ctrl+Alt+End to mimic a Ctrl+Alt+Del, and if the Remote Desktop session is fully screen, then pressing WinKey will operate on the remote system, and Windows Sandbox does appear to use a Remote Desktop frame when it is in fullscreen mode.
How can we pass system keypresses like Ctrl+Alt+Del or WinKey to a Sandbox system instead of the Host system?