Build a docs section with a sidebar

Put docs pages in docs/, with subsections as folders, and give the section a layout that lists its pages:

// docs/_layout.jsx
(content) =>
<>
  <nav class="sidebar">
    <ul>
      {pages("docs").map(p =>
        <li>
          <a href={p.path}>{p.title}</a>
          {p.isDir && p.subpages.length > 0 &&
            <ul>{p.subpages.map(sub => <li><a href={sub.path}>{sub.title}</a></li>)}</ul>}
        </li>
      )}
    </ul>
  </nav>
  <section>
    <h1>{page.title}</h1>
    {content}
  </section>
</>

Pages without a date sort by slug, so to control the order, prefix file names (01-install.md) or sort in the layout by a key of your own, such as order in frontmatter:

pages("docs").sort((a, b) => (a.order ?? 99) - (b.order ?? 99))

A subsection index, such as docs/tutorials/index.jsx, lists its own pages:

data({ title: "Tutorials" });
<ul>{pages("docs/tutorials").map(p => <li><a href={p.path}>{p.title}</a></li>)}</ul>

If docs/ has no index page, send /docs straight to the first page with a line in _redirects, instead of writing a redirect page by hand:

/docs   /docs/getting-started   302