SHOW (fast file and spool browser)
SHOW (aka SHOWFILE by some) is a very fast, very XEDIT-like file browser for CMS. It can read disk files, SPOOL files, and library members. You can write Rexx macros. And it would be fairly easy to extend to other file formats.
Not sure what minimum CMS version it requires, but it's been around pretty long and is quite robust.
(rename file to SHOW MAILABLE after uploading to CMS -- follow instructions at top of MAILABLE file to unpack)