Kotobee Author now supports 19 languages.There is no direct way to add additional languages. However, some of our users have found success in replacing an existing language with their own, by changing all the labels, messages, and commands to their language of choice, then notifying their readers that they’ve replaced language X with their own. 

To customize a language please refer to Customize Language Translations.

If there’s a language you’d like us to add, we’re more than happy to receive your requests.