List only top level categories in advance search

you need to modify template file at events-manager > templates > templates > search > categories.php

to use template: https://wp-events-plugin.com/documentation/using-template-files/

I am not really into coding, any idea what to change in the file?

Regards

you can change the wp_dropdown_categories attributes from https://codex.www.ads-software.com/Function_Reference/wp_dropdown_categories

Thanks, I added ‘parent’ => 0, to the category array and it works perfect.

Kind regards