One of numerous examples is to save and restore
hidden outlines after doing 'revert-buffer':

(add-hook 'Buffer-menu-mode-hook
          (lambda ()
            (add-hook 'revert-buffer-state-functions
                      (lambda ()
                        (let ((regexp (outline-hidden-headings-regexp)))
                          (when regexp
                            (lambda ()
                              (outline-hide-by-heading-regexp regexp))))))))

Currently this handles outlines only in the buffer list.
But probably this settings should be added to outline-minor-mode.

And here is the immediate need to use it to rehighlight the outlines
after reverting the buffer list: