Custom class

Hi guys, I am testibg out your plugin and I really like it so far, I actually designed one website completely with Brizy.

What I would like to know is, does the extra class option in advanced settings of blocks and elements actually work? Because I tried to add the class and then write the code in Additional CSS option that is part of every WP theme but nothing happened.

Am I doing something wrong or is this feature not available at this time?

Thank you!