This is how Github provides Atom and Microsoft is able to support VS Code on all 3 platforms.
The heartbreak of it is that writing Electron menu code still depends in varying degrees on the desktop OS.
There are tons of NPM and other JS packages/libraries that you can glue together to build a desktop app with. Node/NPM in theory promotes small software tools that do a job in the unix commands spirit. I was able to follow a tutorial (a broken tutorial) to build a Markdown Editor that uses the Ace JS editor and some other packages. See https://github.com/chilismaug/wd-markdown-reborn