Feature request: default subtitle language and speed

Often I and my daughter use this amazing site for dig deeper to the Math.. unfortunately, she is so young and she doesn’t understand what shoukd she click when new video with lesson opens. Is it possible to store somewhere subtitle language, which was choosen on the previous video (or making possible to set it in the account settings) As the defaul subtitle language? It would be great! And if it is not too complex, to store somewhere speed of the video (e.g. x0.75)? English language is not native in our country, but learning English from your video will be a golden opportunity for us to be more closer ❤️