Menu: make sidebar menus collapsible

[Blargian]

Summary

Sidebar menu is really overwhelming with the number of items. If we have a more logical structure users will not battle to find where to go and we don't have to show everything.

Checklist

• Delete items not relevant to your PR
• URL changes should add a redirect to the old URL via https://github.com/ClickHouse/clickhouse-docs/blob/main/docusaurus.config.js
• If adding a new integration page, also add an entry to the integrations list here: https://github.com/ClickHouse/clickhouse-docs/blob/main/docs/integrations/index.mdx

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
clickhouse-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jul 20, 2025 7:25pm

3 Skipped Deployments

Name	Status	Preview	Comments	Updated (UTC)
clickhouse-docs-jp	⬜️ Ignored (Inspect)			Jul 20, 2025 7:25pm
clickhouse-docs-ru	⬜️ Ignored (Inspect)			Jul 20, 2025 7:25pm
clickhouse-docs-zh	⬜️ Ignored (Inspect)			Jul 20, 2025 7:25pm

[Blargian]

@dhtclk what are your thoughts on collapsing menu items by default to help reduce the cognitive load on users?

See: https://clickhouse-docs-rnr1vb3j8-clickhouse.vercel.app/docs/use-cases

Another small improvement we can make is to remove the obnoxiously large margin between menu items. See for example the Docusaurus default menu item styling:

My personal feeling is that if content is organised very logically, having the top level items collapsed will be more useful to the user than if they are all expanded.