That's right Garamond and I had forgotten.
You can do this in two ways, the simplest is:
* - Create a new language.
* - Now you need to export independently the files of the translation of XenForo and of the addons installed from old language and import it into the new language.
* - Once it this is done you need to set the new language as default and then you can delete the old language.
But if you want to keep the same ID in the language is necessary to do otherwise
* - First you need to export independently the files of the translation of XenForo and of the addons installed.
* - Now you need to export the language completely, selecting "All" in the moment of exportation
* - Now you need to open the last file exported with an editor (eg Notepad ++)and empty all the phrases of file, leaving the language settings. You'll get something like this:
Rich (BB code):
<?xml version="1.0" encoding="utf-8"?>
<language title="Español" date_format="j M Y" time_format="H:i" decimal_point="," thousands_separator="." language_code="es-ES" text_direction="LTR">
</language>
You can also use this code changing the parameters highlighted in red for the parameters of configuration of your language.
Now you have all the phrases in the master language (English) and the phrases of the addons uninstalled no longer exist in your database. Now you only need to import the phrases of XenForo and of the addons installed.
Please make this check in a test forum before performing in a production forum.