When comparing MultiMarkdown Composer vs IntelliJ IDEA, the Slant community recommends MultiMarkdown Composer for most people. In the question“What are the best Markdown editors for OS X?” MultiMarkdown Composer is ranked 12th while IntelliJ IDEA is ranked 23rd. The most important reason people chose MultiMarkdown Composer is:
Not many popular Markdown editors support MultiMarkdown syntax.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Multimarkdown support
Not many popular Markdown editors support MultiMarkdown syntax.
Pro Multiple export options
You can export to HTML, PDF, LaTeX, RTF, OpenOffice, Microsoft Word, ePub, OPML.
Pro Table of Contents support
Generates a table of contents based on the headers in the Markdown file being worked on.
Pro Support for elastic tabstops
Elastic tabstops are used to align text automatically during writing. When there's a change in the text, MultiMarkdown Composer automatically aligns all lines both on the beginning and end of them.
Pro CriticMarkup support

Pro Optional synchronized scrolling
Hold a key down and get synchronized scrolling.
Pro Fast syntax highlighting
Pro Highly customizable
Pro Counts words, characters, lines
Pro Can show invisible characters
Pro Great Java Support
Pro A good editor for test-driven development
IntelliJ IDEA is really easy to work with when it comes to test-driven development in Java and JavaScript/TypeScript.
Pro Great JavaScript support
Pro Markdown support with preview
Pro Supports PHP quite well
Pro Great TypeScript support
Really good support for importing classes, libraries, etc. into a typescript class. Making it easy to do TDD.
Pro Good BASH script support
Pro Angular CLI support
Pro Made by developers for developers
It can make one more efficient, but also can get one way too used to shortcuts, autocomplete, and easy debugging.
Cons

Con Table of contents gets out of sync sometimes
If you keep the auto-generated table of contents open while you work it gets out of sync, meaning items in the table of contents (at the end) disappear until you restart the program.
Con The way the preview shows images is inconsistent
The preview is a bit inconsistent with images. Sometimes it shows the image correctly, sometimes it shows a blue question mark.
Con Is not free
But it does have a free version (Community Edition).
Con Heavy
Consumes more resources than VSCode etc. But depending on your use-case, it can still be worth it for the benefits you get with this editor.
Con Autocomplete does not work while IntelliJ is indexing
But this, in general, is not much of an issue. Usually after npm install, etc.
