To edit details of a short link, click on the edit icon corresponding to the link.
This opens up a pop-up that displays the current values. You can change any of these and hit the Save button.
The short link is immediately updated and you can then close the pop-up. If you have updated the original link then, users will be redirected to this new link instead of the old one.
If you have edited the backhalf, then the earlier short link will take users to the 404(link not found) page.