Did somebody tried to upgrade the tinymce editor just replacing the "inymce\tiny_mce\3.5.11" folder by a "4.7.13" version and doing some easy things like :
1/ extract standard TinyMCE package into lib/editor/tinymce/tiny_mce/x.y.z/
2/ bump up editor version in lib.php to match the directory name x.y.z
3/ bump up main version.php
4/ update ./thirdpartylibs.xml
5/ execute cli/update_lang_files.php and review changes in lang/en/editor_tinymce.php
etc.