How to create a new localization file?

1. Launch mpTrim.
2. Press 'shift+F12'. That closes mpTrim and creates a new 'English.mpTrim.ini' file.
3. Edit this file with a text editor, and rename it to 'YourLanguage.mpTrim.ini'.

How to update a localization file to a new mpTrim version?

1. Run the new version of mpTrim, using the old localization file.
2. Press 'shift+F12'. That updates the localization file with the new strings.
3. Edit the updated localization file.