The only currency involved in a digital dollar is USD. There is no new currency proposed here.

The thing that makes an existing dollar digital is being in a new type of bank account that is held by the fed instead of a retail bank. So this is an new type of bank account, not a new type of currency.

I do a youtube channel on monetary issues and my last video was specifically on this topic. Feel free to check it out if you are interested

https://www.youtube.com/watch?v=n9qnhV9SAyg