Maybe replace the auto jump button since it's already present in the accessibility settings (so no need to duplicate it Mojang)
Like this?

And then, after clicking on the "Unbound Key" the button/key to unbound should be clicked.

First off, see Klotzi's explanation for how to normally unbind keys :)

Having a functionality like this detached at the top, feels completely counterintuitive to me.
Also, for the reasons I just mentioned in #41 I don't consider the auto jump key to be useless at all.

The best alternative to this would be to change the Reset buttons to Unbind when a keybinding is active (or something like shift is pressed?) but this also feels a little wonky.

What do you want to achieve? If you want a specific keybinding to be unbound then click the edit button and press ESC. ESC is not a valid bound key leading the keybinding to be unbound. This can be done with any keybinding whether it was unbound by default or not.