Many flavors of Markdown support math extensions. Many do so in a way that degrades gracefully when the extended Markdown is opened in a standard Markdown tool.
Typora is a great WYSIWYG Markdown editor that uses MathJax to render LaTeX mathematical expressions.
The problem is, if you do a lot of formula writing in a narrative, most WYSIWYG editors that support LaTeX formula rendering are just not efficient. I want to type my thoughts, start a formula block, write my expression, end the block, and continue going. You can't do that in most WYSIWYG editors.
When I think of WYSIWYG editors, I see presentation and content being mixed.
Unless Typora has figured out how to get remove the need to locate the insertion point of a formula, open an editor, then submit the data to render an image that is placed inline or made into a block. If it has figured that part out then props to them for making it easier to write mathematics in an accessible editor.
Typora is a great WYSIWYG Markdown editor that uses MathJax to render LaTeX mathematical expressions.