Merino is a narrative design tool that lets you write Yarn scripts inside the Unity Editor, built on top of Yarn Spinner and Yarn (a Twine-like script language)
NEWS, 23 Feb 2020: Merino is currently NOT compatible with recent updates to Yarn Spinner (v1.0+)... I'll update it after Yarn Spinner finalizes a lot of stuff, but in the meantime, it doesn't make sense to try to hit a moving target... sorry! ... see https://github.com/radiatoryang/merino/issues/39
download and install from the Releases page;
MIT