A URL scheme parameter that isn’t mentioned in the release notes but that’s been added to Fantastical 2 (and listed here) is add=1, which lets you create a new event or reminder from the URL scheme without having to tap on the “Add” button in the app to save the new item.

This is indeed a welcome addition, and I’ve already rewired my New Reminder action in Launch Center Pro to use Fantastical instead of Drafts. I’m also using the notes flag to throw anything in my clipboard into the new reminder’s notes field. I can copy related text, a URL, or a phone number, then run the New Reminder action, and the related metadata about the reminder gets captured automatically.