In previous versions of Xcode you could preview UI in Interface Builder in another localization by doing this:
1) Open the xib.
2) Open the Assistant Editor and select Preview. Then in the bottom right corner it showed a language, which you could change.
In Xcode 11 is there a new way to do this? Or do I have to change my default language in System preferences and run the app?
Just found it. You can do it now by clicking Editor -> Preview in the menu bar in Xcode 11.