How do you implement URL schemes?

Is this simply not supported (yet) or am I missing something?

This is what I expected. If I click on it, my calendar opens

and this is what I get in RemNote, nothing…

Actually URL schemes mostly work. Here are some examples: Links/Shortcuts To Local Files With Desktop App - #3 by hannesfrank
There are a few cases where the URL is not recognized on pasting, e.g. for devon-think. This is more a bug in the URL regex than a technical limitation.

What happens if you force the link with markdown syntax?

[calendar](calendar://open)

Thanks, that solves the issue. I actually did try markdown before but for some reason you have to copy paste the markdown from somewhere else for it to work, simply writing it down in RemNote does nothing.