Christian Tietze is an author at the zettelkasten.de site and, of course, keeps his notes in a Zettelkasten. He has his own app, The Archive, for that but he’s also an Emacs user. He uses a timestamp as a key to his Zettelkasten notes and can access them from his browser with a URL of the form:
thearchive://match/TIMESTAMP
Being an Emacs user, Tietze wanted to be able to link to his notes through Org mode. To do that, he implemented a special Org-mode link type: zettel. Thus he can use links like
[[zettel:TIMESTAMP]]
or
[[zettel:TIMESTAMP][Descriptive text]]
and clicking on one of them opens the relevant note in his browser.
It turns out to be pretty easy to set this up. Take a look at Tietze’s post for the details. Of course, his is a pretty specialized use case but the same simple procedure can be used to set up your own special links. The post is short and informative so it’s worth taking a look at it even if you don’t need a special link type right now.