This may seem like an unusual request, but markdown just like software code can be formatted automatically by a plugin (like code formatting tools), this helps in adding the right spaces, tabs and lines between items without having to do it all manually.
This overall makes the markdown source cleaner, consistent and more maintainable but of course doesn’t affect the preview at all.
The only reason I’m suggesting this be a feature instead of a plugin, is that I’m not sure if the plugin system will be powerful enough for such auto formatting.
Anyways its just an idea, and a nice to have, can always use other tools to format the source of markdown