In R14 I had a lisp program (ed.lsp) that would open the appropriate editor depending on if I picked text, mtext or attributes.
I am now using LT2008 and alas no lisp allowed. I know you can use the double click on an object, but only if you have noun/verb turned on and I don't row my boat that way, if you know what I mean.
I am thinking that this can be done in diesel. Below is the original lisp file.
;EDIT TEXT OBJECT, ATTRIBUTE, DIMENSION TEXT OR ATTRIBUTE
;ED.LSP (C)1998, By Peter Thomson.
(defun C:ED (/ E ETYPE)
(prompt "\nPick text object or attributed block to edit: ")
(setq E (car (entsel)))
(setq ETYPE (cdr (assoc 0 (entget E))))
((or (eq ETYPE "TEXT")(eq ETYPE "MTEXT")(eq ETYPE
(COMMAND "DDEDIT" E)
((eq ETYPE "INSERT")
(command "ddatte" E)
;End of progam