From the following comp.sys.next.programmer date 12 March 2000. (WebArchive.org (https://web.archive.org/web/20240810231644/https://groups.google.com/g/comp.sys.next.programmer/c/nAqVV1S72f0))
Quote from: Joerg KollmannThe tutorial seems to be written for an older version of OPENSTEP.
Since version 4.2, you shouldn't use the return key as an explicit keyboard shortcut for a button, because you can select buttons using the tab key and then use return to activate the selected button. If you want to use it anyway, you can get the return icon back into InterfaceBuilder's images tab by using Edit.app, opening /NextDeveloper/Apps/InterfaceBuilder.app/Resources/images.plist and adding a line with ",NSReturnSign".
This will be needed to be added to an updated FAQ.