Can it read Hebrew, Japanese (or any other) texts ?

The models are trained on gigantic dataset. Mainly English, but also many other languages. It would be incorrect to state that models support a specific language; they were trained on most of them, and the results depend highly on how much of that language was present in the training dataset. There are no official information about this and the best way is to test it with the AI Playground. Only you can value the quality of the reading/writing ability of the model has with this language.

My language doesn’t seem to be supported, can you add it?

You need to define it in the prompt (or the context, in the case of the chatbot). For example, for the shortcode, the context would be: “Converse in French, as if you were Emmanuel Macron. Be haughty!”

If you are talking about the languages available in the UI of AI Engine (for instance, in the Content Generator), you can actually add it. I am an advocate of clean UI, so I want to enable you to remove the languages you don’t need, and add the ones you need! You can do it this way:

add_filter( 'mwai_languages', function( $languages ) {
  unset($languages['it']); // Remove Italian
  $languages['hu'] = "Hungarian"; // Add Hungaria
  return $languages;
}, 10, 1);

Try to use the proper language code (ISO-639).