As @kbrede wrote, and so much more.
With some RegEx you could e.g. have all undone or undelegated todos shown (so you can actually create a project management system with todos across pages), or only articles that are also tagged drafts but not anything else (so you’d have an instant document management system).
This would pretty much enabled sophisticated quasi saved searches to be embedded within a page.
I’d consider this usage advanced, but highly useful for those who use Obsidian as their primary workspace.
Regarding use cases, this would solve e.g.: