thanks for adding the option to reverse the outline path.  Great thinking about using a different separator for the reversed path!

It mostly works - however, if the window is too narrow, the abbreviation ellipses are now applied to the most recent heading instead of to the last one shown.  It would be better to reverse the outline path before sending it into org-format-outline-path, which also saves you the pain to split and rejoin the path string.

Please find attached a patch that makes this change.  It also removes the dependence on the string library which is, I think, not by default available in Emacs.

Thanks