Add 'searchwp_related_sample_engines' filter to the get_samples function

Meta_Box.php

/**
 * Get associative array of sample results for keywords
 *
 * @param string $existing_keywords
 *
 * @param int $post_id
 *
 * @return array
 */
public function get_samples( $existing_keywords = '', $post_id = 0 ) {
	$samples = array();

	if ( function_exists( 'SWP' ) ) {
		$engines = SWP()->settings['engines'];
	} else if ( class_exists( '\\SearchWP\\Settings' ) ) {
		$engines = \SearchWP\Settings::get_engines();
	}

	if ( empty( $engines ) ) {
		return $samples;
	}

	$engines = apply_filters( 'searchwp_related_sample_engines', $engines, $post_id );

	foreach ( $engines as $engine => $engine_settings ) {

		$post_data = $this->related->get( array(
			'engine'       => $engine,
			's'            => $existing_keywords,
			'post__not_in' => array( $post_id ),
		), $post_id );

		if ( ! empty( $post_data ) ) {
			foreach ( $post_data as $key => $val ) {
				$val = absint( $val );
				$post_data[ $key ] = array(
					'ID'         => $val,
					'post_title' => get_the_title( $val ),
					'permalink'  => get_permalink( $val ),
					'post_type'  => get_post_type( $val ),
				);
			}
		}

		if ( function_exists( 'SWP' ) ) {
			$label = isset( $engine_settings['searchwp_engine_label'] ) ? esc_html( $engine_settings['searchwp_engine_label'] ) : esc_html__( 'Default', 'searchwp-related' );
		} else {
			$label = $engine_settings->get_label();
		}

		$samples[] = array(
			'engine' => array(
				'name'  => $engine,
				'label' => $label,
			),
			'samples' => empty( $post_data ) ? array() : $post_data,
		);
	}

	return $samples;
}