If you're looking to send out a mailing and am not comfortable using the method outlined in the Community post you referenced, you can use the Insert button in the Style Bar to insert a customizable bullet point. Please note that the spacing for this inserted bullet point will not automatically indent. Alternatively, you can create the custom bullet points in another program, such as Microsoft Word, take a screenshot of the bullet points, and upload it to an image block in your campaign.
I hope this helps! Please let me know if you have any questions.