Interesting thought for the use of markdown and compatible files (canvas, bases, excalidraws, etc > based on my experience using Obsidian) that are stored locally.
The apps, that interpret these files and displays them in a GUI, could serve different purposes like nostr clients can focus themselves on using specific kinds. But in the end all the files are interoperable in the different apps.
Example:
1. Obsidian (hub = storing and displaying all file types)
2. An app kinda like Goodnotes for iOS (for using excalidraw files)
3. An app for bookmarks (instead of saving and editing them manually in all the browsers I use. They could be stored in one place. Certain links are openend in a pre-destined browser and other links are open to choose natively or with an application chooser like Junction)