I setup org-timer indicator in mode-line with this.

(setq-default
 mode-line-format
 (quote
  (
   ;; org-timer
   (:eval
    (unless (not org-timer-countdown-timer)
      (propertize (let* ((rtime (decode-time
                                 (time-subtract
                                  (timer--time org-timer-countdown-timer)
                                  (current-time))))
                         (rmins (nth 1 rtime))
                         (rsecs (nth 0 rtime)))
                    (format "🕔 %d:%d" rmins rsecs))
                  'face '(:foreground "cyan" :weight bold)
                  'help-echo "org-timer")))

   )))


I hope this org-time indicator only show in active mode-line instead of all
mode-lines.

I hope to find a general way which can add any extra indicator not just
org-timer. I can just put my upper code without too much modification into
that general way.

I also posted a post on Emacs.SE
https://emacs.stackexchange.com/questions/26222/how-to-only-show-thing-in-active-mode-line-instead-of-all-mode-lines

How to do it?

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