Need to enable "always listen for hey siri" in shortcuts

When I go to sleep, I usually turn off all lights in my room, and use iPhone's back light when I sometimes need to temporarily leave my bed. I turn on the back light using Hey Siri. And I have to put my iPhone facing down so that black light is not covered. I also need to enable "Always Listen for Hey Siri". I try to create a Shortcut to automatically enable it when I enter sleep mode. But I can't find such action.

Can we ask Apple to add such action?