A quick orientation to what the panel covers before you dive into the details below.
Drop the component in, pass your sections, and the rail wires itself to the scroll position.
The active link tracks whichever section sits in the middle of the viewport as you scroll.
Everything is plain class names and inline color, so it adapts to whatever surface it lands on.
Click any link to glide to its section; the rail and the content always stay in sync.