[Plugin: Events Manager] Category Slug

please see this docs

-https://codex.www.ads-software.com/Taxonomies
-https://codex.www.ads-software.com/Function_Reference/get_term

then you can create your own placeholder – https://wp-events-plugin.com/tutorials/create-a-custom-placeholder-for-event-formatting/

I also needed of this and I’ve found to solution, so I post it for those who want to know much :

add_filter('em_event_output_placeholder','my_em_styles_placeholders',1,3);
function my_em_styles_placeholders($replace, $EM_Event, $result){
	global $wp_query, $wp_rewrite;

	switch( $result ){
		case '#_CATEGORYSLUG':
			$replace = 'none';
			$event_category_id = $EM_Event->get_categories()->get_ids();
			$event_category_slug = $EM_Event->get_categories()->categories[$event_category_id[0]]->slug;

			$replace = $event_category_slug;

			break;
	}
	return $replace;
}

thx for sharing!