Hello,
currently my login on myopenhab.org is my e-mail address. I’m planning to clean up my old emails.
So my question is simple - is there possible to change the login (login is my email) or need I to create new user with news login?
You can change the email.
Log into myopenhab.org and navigate to Users.
I recommend creating a new user with the new email and testing that it first to make sure it works as needed. Then you can delete the old one.
Make sure to set the new user with role “Master”.
Haaaa! Very good hint!
I thought only the original user as first master could log in to myopenhab.org and manage users.
It works! 
Thank you so much!