Hello!

How to create a new DB for a slave site? I enter:
DB host: localhost
DB name: city
DB prefix: city_
DB user: root
DB password:
(password is empty)

I click to "Save" and see an error: Database Error: Unable to connect to the database:Could not connect to database.

I open a file multisites.cfg.php and enter:
define( 'MULTISITES_DB_GRANT_HOST', 'localhost');
define( 'MULTISITES_DB_ROOT_USER', 'root');
define( 'MULTISITES_DB_ROOT_PSW', '');

Where is an error?
Or I have misunderstood also a database it is necessary to create independently through phpMyAdmin.

As the PSW is empty, if you have entered a PSW somewhere else, it will probably use the password your DB to copy or new DB to copy.

I suggest that you create a specific "root" user with a password.