Enqueue Child Theme’s CSS & Additional CSS in WordPress Editor

/* Enqueue Child Theme style.css to editor */

add_filter('block_editor_settings_all', function($editor_settings) {

    // Get the URL of the child theme's style.css

    $child_theme_style_url = get_stylesheet_directory_uri() . '/style.css';

    $editor_settings['styles'][] = array('css' => wp_remote_get($child_theme_style_url)['body']);

    return $editor_settings;

});

/* Eunqueue Customizer CSS to editor */ 

add_filter( 'block_editor_settings_all', function( $editor_settings ) {

    $css = wp_get_custom_css_post()->post_content;

    $editor_settings['styles'][] = array( 'css' => $css );

    return $editor_settings;

} );