Huge +1 from me too! I’ve only recently started using Obsidian after switching over from Joplin, and it is absolutely amazing!
I use NotePlan for Markdown notes and todos, and it has a great x-callback-url API: https://noteplan.co/faq/General/X-Callback-Url%20Scheme/ that allows any app to open a note in Noteplan from a URL like noteplan://x-callback-url/openNote?noteDate=20180204
If Obsidian did the same, note only would Obsidian be able to open NotePlan’s notes dir and visualise the graph, but Hook could glue the two together and allow NotePlan to open pages in back in Obsidian.
That would be an unparalleled level of Markdown knowledge management awesomeness!