In case you are crazy enough to still run OS/2 and need a hex editor, here is one :o)
I wrote this sometime between 1994 and 1997, probably under OS/2 Warp 3. Thought I had lost the code for good, until I stumbled upon an old backup just now. Also contained a built .exe which I'll upload under releases.
I don't remember what the state of the code was, or if it's even the most recent version, but I tested it in a VM running OS/2 Warp 3 and it seems to work fine.
Even lets you switch between file contents and extended attributes. (Yay HPFS)
NOTE: The editor will neither warn you before overwriting an existing file with "Save as...", nor will it warn you before closing/exiting with unsaved changes! For grown-ups only.