A lot of Markdown editors exist, and your choice depends on the platform (Win/Mac/Linux), the features you want and the technical skills of your end-users.
I’m using Vscodium with a bunch of extensions and tweaks, but I bookmarked these Apps, which could be easier to use:
- GhostWriter: ghostwriter
- Notable: https://notable.app
- Joplin: https://joplinapp.org
See also this previous post on the same topic: Desktop CMS/GUI App for Hugo?