When porting an old Mac project to Silicon (universal) I got an issue with IB to open MainMenu.xib:
Trust opening older file format? “MainMenu.xib” uses an older format that is potentially insecure when decoded.
If you trust the content of this file, open and save it to upgrade to the modern format.
The "open and Upgrade" button make the MainMenu.xib not editable: it seem that every submenus has disappeared.
How can I fix it ?
Any suggestion will be greatly appreciate.