CKEditor is the software component underlying Tiki's WYSIWYG editor. Tiki uses CKEditor 4.
CKEditor 5
In 2018, a new major version of CKEditor was released, CKEditor5. This release brings massive changes which would benefit Tiki, but the new version is no longer licensed under the LGPL. A discussion about whether a migration to CKEditor 5 can happen despite this change has started.
Source / debugging
Even when Tiki's JavaScript minification preference is disabled, the CKEditor files served by Tiki are compressed to avoid performance issues. Consequently, stepping into these files with a debugger is largely useless.
Replacing these minified files with original CKEditor sources can be achieved with a POSIX shell and Git following the fairly simple procedure documented in this comment , for CKEditor profile standard-all. As of Tiki 18, the CKEditor version is 4.5.6. The vendor/ckeditor/ckeditor/ must be replaced with the ckeditor/ directory generated. On a system with the required dependencies, all of this should take about 15 minutes.
The result of this compilation for CKEditor 4.5.6 (used by Tiki 15) is attached to this page.