Editus Version 0.9.13.0 now supports WordPress built-in REST API. (Introduced with WordPress v. 4.7)
Editus now checks if any other user has the post opened for editing, and will prevent you from editing in that case.
Also, in addition to “Ignored Items” you can also specify “Read Only” items that are parts of the post content but should not be edited. You can also show the “Ignored Items” and keep them read only instead of removing them from the view while editing.
More work is ongoing to improve interoperability and usability. Happy Holidays!