The default way of redoing the previous command from the command history is via :redo. If you want to use ! (exclamation mark) instead of :redo, add the following to your .lispworks file:
(set-macro-character #\!
#'(lambda (stream char)
':redo))
You may wish during some sessions to reset ! back to its normal role as a character. To do this, evaluate:
(set-syntax-from-char #\! #\@)
LispWorks User Guide and Reference Manual - 13 Feb 2015