The other day I followed an HN link and downloaded https://www.zettlr.com/ . It's "basically" a manager of Markdown files, and its syntax highlighting was compatible with the Hugo Markdown syntax. For a minute I wondered if I could take the source code of the editor and make it understand my Hugo-specific shortcodes (I put up a lot of pictures so I have homebrew {{ <gallery> }} and {{ <figure> }} shortcodes), but that's in my ever-extending "To Do Someday" list.

The idea would be: it would read the Markdown as I write it, let Hugo render it, and return the HTML to be rendered in the editor window.

Looking at your editor, it really looks like Zettlr (I'm guessing they're both Electron apps).

I guess you have 2 almost separate problems: the editor and the hosting. On the topic of hosting, I guess if a "blogger" can get his own domain name, the actual infrastructure can be swapped under it (and the data republished from the local machine), as long as the reader can load the blog using the known URL, it's fine.