multiple language settings

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This script is a life-saver. Thank you. It would be nicer if I can choose a language from a list of languages on the go and add multiple subtitles to the video.

My main use case is to learn foreign languages. I would like to see two subtitles. The language of the first subtitle is my native language, and the language of the secondary subtitle is the language of the video.

I think I need to retain the current subtitle, cycle the language list and add a secondary subtitle.

Can you please implement that?