You don’t have to do anything in the fs2020 controllers section.
Once the quest 2 is connected to your computer (airlink or cable) you should be able to switch fs2020 into VR mode using the default key binding Ctrl + Tab.
First make sure you have a Quest 2 connection to your computer.
This article explains it for airlink (which works and feels better than a cable if you have a good router.)
BTW, the reason you’re getting “you are trying to assign an action to a device that is not detected”
is because you are trying to bind Ctrl + Tab to your mouse.
You should chose keyboard first in the controllers options tabs.
But again, no need to change anything here.