Expandable vertical navigation concept

Objective

Inside top-level pages, readers need local navigation without seeing every page in the entire site.

Behavior

• Show only the current major section in the left rail.
• Current group is expanded by default.
• Other groups are collapsed and show a count.
• A section should fit in one viewport at 13-inch laptop height.
• On this page right rail shows only H2 headings for the current article.

Desktop layout

Top horizontal nav
--------------------------------------------------
Left local nav | Article content | On this page

Mobile layout

Top bar
[Section menu] [On this page]
Article content

Local nav example

Learn 101
  ▾ Start here
    What is Fleet?
    Install locally
    First job
  ▸ Studio and Admin (2)
  ▸ Troubleshooting (1)

Accessibility

• Use <button> for disclosure controls, not clickable divs.
• Maintain aria-expanded and aria-controls.
• Preserve focus order.
• Escape closes dropdown/drawer where implemented.
• The current page link has aria-current="page".
• The section nav is labelled with aria-label="Learn 101 navigation".

Acceptance

• Left nav does not exceed the viewport for common page sizes.
• No page exposes the full 50+ page site map in the default viewport.
• Keyboard navigation can expand/collapse groups.
• Active section and active page are visually clear.