transient transient mark mode does not highlight region

[Samuel Wales]

I use c-spc c-spc to temporarily activate transient mark mode.

However, for example, if I c-y into org mode, I might like to demote
the region.  But that only works if the region is highlighted.  And
there is no way to do c-spc c-spc c-x c-x and have the region
highlighted.

Is there a way to make, say, c-x c-x highlight the region as if it
were transient mark mode?

Thanks.

P.S.  I found that this did not work:

;;;(substitute-key-definition 'exchange-point-and-mark
;;;                           'alpha-exchange-point-and-mark
;;;                           global-map)
;;;(defun alpha-exchange-point-and-mark ()
;;;  (interactive)
;;;  (let ((transient-mark-mode t))
;;;    (exchange-point-and-mark)))

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