Editing the dynamic hyperlinks in ArcMap's Dynamic Hyperlinks Dialog has no effect.
This is a known issue.
Solution or Workaround
To make a change to an existing hyperlink from the Dynamic Hyperlinks dialog, remove the link and then add the edited link.
- Select and click the link to make the text editable.
- Use Ctrl-C to copy the text from the link.
- Click the Remove button to remove the link.
- Click the Add new button to create a new link. Use Crtl-V to paste text into the link.
- Make any needed edits to the link text and click OK.
For more information on how to create hyperlinks in ArcMap, please refer to the ArcGIS Desktop Help.