From the FAQ page:
In the Draft.js editor type >! on a new line, then press space, then a spoiler box should appear In the Markdown editor, surround your text with :::spoiler at the beginning, and ::: at the end.
In the Draft.js editor type >! on a new line, then press space, then a spoiler box should appear
>!
In the Markdown editor, surround your text with :::spoiler at the beginning, and ::: at the end.
:::spoiler
:::
From the FAQ page: