wanted "most recent before current"-window. get-mru-window gives current. instead of simplest, i did the most complex thing that could work. almost.

gistfile1.el

(defun windows-in-use-time-order (&optional old-to-new windows)
	"Windows sorted by their `window-use-time'.
Without arguments windows on current frame ordered from most to least recent.

Optional argument OLD-TO-NEW with non-nil value reverses the order.

Optional argument WINDOWS specifies which windows to sort by use time:

- a list is assumed to contain windows and sorted

- a function is called, should return list of windows to sort

- any other value is passed to `window-list-1' as ALL-FRAMES parameter"
	(sort* (cond ((and windows (listp windows)) windows)
							 ((functionp windows) (funcall windows))
							 ((window-list-1 nil 'nomini windows)))
				 (if old-to-new '< '>)
				 :key 'window-use-time))

;; to get the window that was used before current on, in current frame:
(nth 1 (windows-in-use-time-order))

;; in all frames:
(nth 1 (windows-in-use-time-order nil t))