um-groups-bb-compatibility.php

function dgtl_filter_hidden_groups( $query_args ) {
	if ( 'um_groups' == $query_args['settings']->post_type ) {		// if the post type selected is 'um_groups'
    		$query_args['meta_key'] = '_um_groups_privacy';			// and custom field '_um_groups_privacy'
		$query_args['meta_value'] = 'hidden';				// and field value 'hidden'
		$query_args['meta_compare'] = '!=';				// are not equal
	}
    return $query_args;								// only show public & private groups
}
add_filter( 'fl_builder_loop_query_args', 'dgtl_filter_hidden_groups' );