looked around how to change the admin credentials, but still confused.
What to do to change the password of an existing admin? Reset the password or change it in the server.properties?
How to make another user be able to use the admin dashboard (https://IP:9443/admin)? Change in the server.properties or also in the .user file associated to the user?
OK. Managed it.
How did you manage it?
@Costas: created a new account; changed this account properties in the .user file (SuperUser: true), deleted the old admin account .user file and also changed the server.properties file inserting the new account details.