As noted before in the forums, add ?reveal=1 to the end of an item link to show it in its current location.
This is also fully covered in the Help > Documentation > Automation > Item Links** section.
Aa new window will be opened but it will be a main window with the file selected in its current location when you use the reveal parameter. Otherwise a document window for the file is opened.
Interesting - I migrated from OmniFocus but I still have OmniOutliner installed. I can’t duplicate the problem. Are you editing the actual link, or the text that you click?
Move your cursor into the underlined link and hit command-K. That should let you edit the target of the link.