Folding it away

Let readers fold the whole list adds the Show/Hide control. Start folded on small screens is on by default: a long list on a small screen pushes the article itself off the bottom of the screen. The list is folded from the first moment the page appears, so nothing on the page moves when it finishes loading. Neither setting applies to a list whose folding is switched off in the block or with [toc collapsible="no"].

Without JavaScript nothing can be folded or unfolded, so the list is shown open and the Show/Hide control is left out.

A folded list is hidden from the keyboard and from screen readers as well as from sight, so nobody tabs into links they cannot see.

Let readers fold each branch applies to the nested layout. Open one branch at a time turns that into an accordion.