Quick Edit and Bulk Edit for a Custom Field

// Custom field and its label.
$wpide_qe_key   = 'subtitle';
$wpide_qe_label = 'Subtitle';

add_filter( 'manage_post_posts_columns', function ( $columns ) use ( $wpide_qe_label ) {
    $columns['wpide_qe'] = $wpide_qe_label;
    return $columns;
} );

add_action( 'manage_post_posts_custom_column', function ( $column, $post_id ) use ( $wpide_qe_key ) {
    if ( 'wpide_qe' === $column ) {
        // The hidden span feeds the Quick Edit box.
        $value = (string) get_post_meta( $post_id, $wpide_qe_key, true );
        printf( '<span class="wpide-qe-value">%s</span>', esc_html( $value ) );
    }
}, 10, 2 );

$wpide_qe_box = function ( $column, $post_type ) use ( $wpide_qe_label ) {
    static $printed = array();
    if ( 'wpide_qe' !== $column || 'post' !== $post_type || isset( $printed[ current_action() ] ) ) {
        return;
    }
    $printed[ current_action() ] = true;
    printf( '<input type="hidden" name="wpide_qe_nonce" value="%s">', esc_attr( wp_create_nonce( 'wpide_qe_save' ) ) );
    printf(
        '<fieldset class="inline-edit-col-right"><div class="inline-edit-col"><label><span class="title">%s</span><span class="input-text-wrap"><input type="text" name="wpide_qe_value" value=""></span></label></div></fieldset>',
        esc_html( $wpide_qe_label )
    );
};
add_action( 'quick_edit_custom_box', $wpide_qe_box, 10, 2 );
add_action( 'bulk_edit_custom_box', $wpide_qe_box, 10, 2 );

add_action( 'save_post', function ( $post_id ) use ( $wpide_qe_key ) {
    if ( ! isset( $_POST['wpide_qe_nonce'], $_POST['wpide_qe_value'] ) || ! wp_verify_nonce( sanitize_key( $_POST['wpide_qe_nonce'] ), 'wpide_qe_save' ) || ! current_user_can( 'edit_post', $post_id ) ) {
        return;
    }
    $value = sanitize_text_field( wp_unslash( $_POST['wpide_qe_value'] ) );
    // Bulk edit with an empty box keeps existing values.
    if ( '' === $value && isset( $_REQUEST['bulk_edit'] ) ) {
        return;
    }
    update_post_meta( $post_id, $wpide_qe_key, $value );
} );

add_action( 'admin_footer-edit.php', function () {
    ?>
    <script>
    jQuery( function ( $ ) {
        if ( ! window.inlineEditPost ) { return; }
        var original = inlineEditPost.edit;
        inlineEditPost.edit = function ( id ) {
            original.apply( this, arguments );
            var postId = typeof id === 'object' ? parseInt( this.getId( id ), 10 ) : id;
            var value = $( '#post-' + postId ).find( '.wpide-qe-value' ).text();
            $( '#edit-' + postId ).find( 'input[name="wpide_qe_value"]' ).val( value );
        };
    } );
    </script>
    <?php
} );