I localized a part of my application with creating a base.lproj storyboard and 3 string files for it. It was a month ago and after that I added new view controller to app, b
Xlifftool is available as a Mac app and works well. It shows all the translatable strings and objects from info.plist, localizable strings, and the storyboard.
Get it here for the mac: https://itunes.apple.com/lv/app/xlifftool/id1074282695?mt=12
Step 1: in Xcode, select your project folder in the project navigator. Then select Editor/Export for Localization...
Your translatable strings will be included in an xliff file under the language you selected for localization in Xcode.
Step 2: Open that file with xlifftool and translate or update your translations there were done previously.
Step 3: Then upload back into your project with Editor/Import Localizations...