I can't find where in the codebase they employ contentEditable. Are you sure they still use it? Here is a GitHub search: https://github.com/ckeditor/ckeditor5/search?utf8=%E2%9C%93&...
3 Markdown documents, one JSON doc.
3 Markdown documents, one JSON doc.
[1]: https://docs.ckeditor.com/ckeditor5/latest/examples/builds/c...