Doing Options → Options and clicking on Language displays this pane:
The current language is shown in green near the lower right of the pane.
To choose a language for the Koda GUI, select it and click on Apply.
If a help file is available for this language, Download help file will be enabled. Click on this button to install it.
To add a new language file,
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If you need to change the flag icon, please download language kit from Koda's homepage.