Hi,
I created some extension for JDeveloper which allows to edit files in hexadecimal editor.
https://github.com/exbin/bined-jdeveloper-extension
Original plan was to support also editing of BLOB/CLOB columns in database for SQL Developer, but I was not able to figure that out yet. Maybe in some future release.
Even thou it's very basic/limited, It would be great if it could be added to page with 3rd party extensions: https://www.oracle.com/ocom/groups/public/@otn/documents/webcontent/130355.xml