I've put some thought into how cool it would be to have a feature similar to Notion databases within Obsidian; probably not integrated into the markdown document, but similar to their new Canvas feature, separate files next to markdown documents which map to SQLite databases with a standard schema that you can browse right within Obsidian. Feels like something an add-on could exist for, but doesn't; and/or I hope its something the Obsidian team is thinking about now that Canvases are shipped.