Here you can find common settings for all user directories.
Login translations
If you want to customise login button/select translations that are visible to user when selecting or signing in via this directory, you can do that in Login translations tab.
Directory login captions can be added for every language / locale you need, just press Add button and select appropriate language and country. In most cases, it is useful to only select translation language and leave country unselected unless you really need different translations for, for example, British and American English.
Directory login descriptions are currently not used but maybe used in future to provide additional details about this directory.