I always did this with a plug-in that semi-decently rendered MD from a Google doc, but i couldn't go round trip.
Now it looks like MD support will be built in
https://www.ghacks.net/2026/10/06/google-docs-adds-native-markdown-file-editing-with-rendered-md-previews-in-google-drive/
I've never cared for MD. I favor ubb code.
Not my favorite but it has wide adoption so if you want all the writing tools of Docs like spelling and grammar correction, it's nice to have that and then export something clean to a CMS that can handle MD, which most do with an add-on
OTOH if you want to compose in a simple text editor distraction free and import to have the tools, you can put formatting in on the fly.
Fundamentally I'm lazy and prefer WYSIWYG.
But I did for a while compose in Docs and export MD and then import that into WP as my standard workflow because that allowed me to keep basic markup without importing all manner of junk formatting