Hi, thank you for your insights and guidance in this matter. I tried to follow the bug ID FB12042397 but does not exists anymore. I am wondering if that bug/API limitation still exists, or it has been fixed already. Thanks in advance.

The workaround is to manually write the new IBOutlet property/IBAction method manually in code - paying attention to the actual IB element's class and signature. Then it is possible to create the link from the relevant gutter or by using the Connection Inspector or by right-clickling the IB element and dragging the relevant event or referencing outlet from the appearing popup window into the File's Owner icon in the View Controller which is somehow quicker. For those looking for "File's Owner" it is the first yellow round icon on the selected View Controller top-bar which appears only when the VC is selected. The other two orange ones being First Responder and Exit. Clumsy :(