In your articles, use the following to insert each type of callout as needed into the source code:

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<div class="note important></div>

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Just know that the note callout box won't show up in your Zendesk article draft. It'll only show on the end user pages when you preview or publish the article.

https://support.zendesk.com/hc/en-us/articles/4408829627930-How-can-I-format-the-text-of-the-article-with-the-source-code-

https://support.zendesk.com/hc/en-us/community/posts/4408860577178-Tips-and-Notes-Boxes