### Summary In the left sidebar navigation, when a section with sub-items is expanded (for example, "Installation"), clicking its downward-facing arrow again does not collapse the section. Users naturally expect an expand/collapse toggle arrow to work in both directions — even if this is intentional (e.g., to keep the active page's context visible), it hurts the UX since users assume clicking again will close the dropdown. ### Page https://react.dev/learn/installation ### Details **To Reproduce** 1. Go to any documentation page with an expanded sidebar section, such as https://react.dev/learn/installation. 2. Locate the left sidebar navigation. 3. Click on the downward-facing arrow next to the currently active/expanded section (e.g., "Installation"). 4. Notice that the section does not collapse as expected. **Expected behavior** Clicking the dropdown arrow of an already expanded section should toggle it back to a collapsed state. **Desktop:** - OS: Windows - Browser: Chrome **Additional context** Observed on the main react.dev documentation site. Fixing this would make the navigation feel more intuitive and aligned with standard UI patterns for accordions/dropdowns.