Elite Controller Back Paddles Do Not Show Up In The Button Test

What you are seeing is correct, and once you know why, the paddles become very flexible for your brother.

The Xbox controller standard on Windows, XInput, defines a fixed set of buttons, and browsers use a similar fixed layout of 17 buttons. Neither has a slot for a paddle. So the Elite does not report paddles as new buttons; each paddle sends whatever existing button you assign to it. Unassigned, a paddle sends nothing. Assigned to A, it sends A, and the button test shows A lighting up.

That is also the right way to test them: assign each paddle to a different button, press it, and confirm the expected button lights. It proves the switch under each paddle works.

For limited hand mobility, the useful idea is to move frequently used actions to wherever is easiest to press. If the face buttons are hard to reach, put the most used actions on the paddles. If the triggers are hard to pull, their functions can be mapped elsewhere too. Profiles let you keep a different layout for each game and switch with the profile button.

Run the button test after every change to confirm the controller sends what you intended. If you later need more inputs or switch-based play, the Xbox Adaptive Controller is designed for exactly that.