I dont know if this counts
You'll have to wait 90 days after your last username change to do it again.
https://support.chess.com/article/493-how-can-i-change-my-username
You might be able to get support to do it before then but there's no guarantee.
https://support.chess.com/collection/343-contact-us
If you need help, please contact our Help and Support team.
I want to change my username from just-playing-chess12 to lord of cinder