In addition to the three elements in the Locale we added a fourth element to be able to override the official translations from the application with a customized version. It is very common that you want to have some parts translated differently, for example on the login screen. You could change this translation in the OLAT translation files, but when updating to a new release all your modifications would be lost. This is where the Brasato i18n overlay mechanism comes in.

In your user space directory (normally this is the olatdata directory) you will find a directory olatdata/customizing/lang/overlay. In this directory you can add the language overlay files for each language. The file name consists of the locale that is overridden and the name of the overlay. The package/bundle structure must be the same as in the source code, e.g. you would add olatdata/customizing/lang/overlay/org/olat/core/_i18n/ and add your customization file there.

LocalStrings_de__customizing.properties : this file would override the language de. In this example, the overlay is named customizing (default setting). This can be configured in the I18nModule. Note that you don't need to translate everything to use the overlay feature. It is perfectly okay to have only one overlay file with only one key in it. For all other keys the normal translation would be used.

No worries, you don't have to do this manually, just use the online language customization tool and everything happens automatically.