URL:https://boostnote.io/#download
For code snippets the app is able to highlight code syntax in more than 100 languages, including Javascript, Python, HTML and CSS and you can store multiple code snippets within the same snippet."
This software is available for all major OS.
Ref: https://stackoverflow.com/questions/41604263/how-to-display-local-image-in-markdown
Ref: https://wordpress.com/support/markdown-quick-reference/
It can be done using plugin for Visual studio code.
Ref: https://stackoverflow.com/questions/11948245/markdown-to-create-pages-and-table-of-contents
https://boostnote.io/#download