Customizable Right Side Panel: <Panel /> coexist with TOC

[HadesArchitect]

Problem

Currently, the <Panel> component replaces the Table of Contents when used (docs). This makes it an either/or choice — you get a custom panel or a TOC, but never both.

Right Panel takes precious screen place but it's value is restricted.

See example: supabase docs have Right Panel with video, feedback AND TOC.

Proposal

Allow Panel and TOC to coexist

Let authors add custom content to the right side panel alongside the TOC rather than replacing it. For example:

• A mode or prop on <Panel> like <Panel position="above-toc|below-toc"> or <Panel replace="false"> that renders custom content above/below the TOC instead of replacing it.
• Alternatively, a dedicated <SidePanel> component that appends to the right column without touching the TOC.

This would be useful for pinning contextual info, links, or callouts while still giving readers the navigation benefits of a TOC.

Why this matters

More flexible layouts — many docs benefit from pinned side content (quick references, related links, warnings) without sacrificing TOC navigation.

Related Proposal

https://github.com/orgs/mintlify/discussions/3505