Assigning classes to elements.

Hi, I often use a script in my functions.php to assing a class to the Extended Layout’s container modules…
add_theme_support('avia_template_builder_custom_css');
This function , though, does not create a class inside the proper element but in its parent container.
Is there a way to assign it to the real element so that if I have 3 titles or 3 images in a flex_column each one of them can have its own class?
Thank you.