CiviCRM Community Forums (archive)

In the download with the translations are files like civicrm_data.nl_NL.mysql

They are only used for new CiviCRM installations, to fill the values for the data in the database.
If you forget to install the file before installing civicrm you will have no other solution as a re-install (if you want to use another language).

Making a translation is difficult to do in one time before you see the results on the screen. Is it possible to add files to the translation download?

The first installation can be in UK, and the other files are not installing the data but are used for migrating to another language. I have made two files (for NL and for UK, to change back). They are only for new installations and for version 2.2.
The files can be executed by phpmyadmin or mysql.exe.