Force the inclusion of CSS for certain elements within the Critical CSS function of SWIS Performance

swis-critical-css-api-override.php

<?php
/*
Plugin Name: SWIS Critical CSS Override
Version: 1.0.0
*/

add_filter( 'swis_generate_css_post_fields', 'swis_ccss_override_post_fields' );
function swis_ccss_override_post_fields( $fields ) {
	if ( is_array( $fields ) ) {
		$fields['forceInclude'] = array(
			array( 'value' => '.wp-block-embed__wrapper' ),
			array( 'value' => '.wp-block-cover' ),
			array( 'value' => '.wp-block-cover-image' ),
		);
	}
	return $fields;
}