How do I import a multimarkdown file and have scrivener replace the tags with their formatting counterparts? For example, this in the source file will be replaced with this after scrivener converts it.
I would convert the document to a word processing file using MMD, there is going to be no better way of doing it than that. Scrivener itself is designed for using MMD in Scrivener just like you would use it everywhere else, not as a replacement for that method of writing, so it has no mechanisms for working the way you describe.
Thanks.