Tab key is both a control character moving the cursor to the next input and also an input representing the tab character as you see in a text editor.

Now that im thinking about it I’m convinced capslock would have been superior next field key and alt+capslock to be used for toggling capslock. But it’s not obvious to me capslock [e: must be] seen by the OS. It could be changed on the keyboards themselves.

It definitely is visible, OS login screens usually warn you if caps lock is on when typing password