Using the online editing function of GitHub, Hugo sites become “real” CMS-Systems.
GitHub allows you to edit the content repos you have write access to via their webpage. (look out for the pen symbol!)
For saving, GitHub generates a new commit directly in the GH repo.
This can be used for online-editing of the hugo sites. To try this out, you need to fork one of the examples - as you will need to edit the repo! Find the github repo url in the config and set it to your correct repo name.
With a pages build and deploy on each push in place, the site will automatically updated after such a change.
The Docsy Theme makes good usage of this, it even allows to create new pages! See for example https://about-hugo.github.io/theme-tryout-docsy/blog/
The Minimal-Site example also has edit links for each part of the site structure.