There’s currently no native element for a persistent, collapsible side panel that can expand/collapse (including to an icon-only rail) while remaining part of the page layout.
An additional toggleable element could be added: Collapsible Side Panel (also referred to as Collapsible Sidebar or Navigation Rail).
Some benefits would be:
- Enables modern UI patterns we’d currently have to approximate with custom CSS/JS or rigid columns (dashboards, documentation sidebars, persistent filters, YouTube-style navigation, tool panels, etc.).
- Complements existing toggleables without overlapping them. Off Canvas remains temporary/overlay, while the Side Panel is co-planar and persistent.
- Reduces reliance on workarounds.
- It’s a very common modern layout need, and Cornerstone could cover it with this element.
Features it could have:
- Expand / collapse states (full content vs icon rail / minimal width)
- Built-in collapse toggle with flexible positioning
- Layout modes: push page content or overlay page content
- Independent width controls for expanded and collapsed states
- Sticky / fixed positioning options
- Responsive behavior (auto-collapse below a breakpoint, similar to the stacking option in tables, or convert to Off Canvas on mobile)
- Optional state persistence (remember user preference via localStorage)
This element would fill a clear gap in the current toggleables suite and give us a clean, powerful way to build persistent side navigation and tool panels.