I was testing the new Gutenberg editor for Wordpress, and realized that this kind of approach to edition would be interesting for one of my custom (non-Wordpress) PHP projects.
It's for a small newsletter system, so the goal is to allow people without specific knowledge in HTML/CSS to easily generate and edit (semi-)rich content built on specific HTML/CSS code (since your standard HTML for the web often doesn't work well in email).
I'm guessing that Gutenberg was developed specifically for Wordpress and is deeply integrated to it, which probably makes it very difficult to reuse in another system.
Are there other similar solutions available, that can be injected and customized into any project? Not just a standard WYSIWYG JS editor (like TinyMCE), but something that works in its core with this concept of reusable predefined blocks, that can be inserted, edited, moved around, etc.