Is there a tool (application, online service) that helps writing the ugly formatting MathJax + mhchem code? I mean things like just typing Ctrl-B to get the selected text to bold is something else then typing $\ce{}$ to get H2O as $\ce{H2O}$

I do not mean a WYSIWYG editor like the onsite one, or stackedit.io (MathJax only). I mean the help with actual writing the formatting metacharacters. Like macro expansions, buttons for formatting or similar.

As the requirements for a fancy, typographically correct text does not seem to be balanced with the support of available editor tools.

I do not think MathJax + mhchem is difficult. Just boring and inconvenient to write the code, so any tool help is welcome.

The drawback of the extensive MathJax formatting by others, even if well intended, is, that one may not be able to edit his own formulas anymore. As they may become so complicated one may lose the track of the formula structures and hierarchies, getting into code pairing hell. :-(

I suppose such formatting should not be done soon after last editing, in case the question/answer author is going to update the text.