主力是WP_Theme::get_page_templates() （由helper函数包装get_page_templates()). 如果您签出源代码，您将看到：

/**
 * Filter list of page templates for a theme.
 *
 * @since 3.9.0
 * @since 4.4.0 Converted to allow complete control over the `$page_templates` array.
 *
 * @param array        $page_templates Array of page templates. Keys are filenames,
 *                                     values are translated names.
 * @param WP_Theme     $this           The theme object.
 * @param WP_Post|null $post           The post being edited, provided for context, or null.
 */
return (array) apply_filters( \'theme_page_templates\', $page_templates, $this, $post );

function wpse_226324_page_templates( $templates ) {
    // Remove tpl-home.php template
    unset( $templates[\'tpl-home.php\'] );

    // Add custom template
    $templates[\'tpl-custom.php\'] = \'Custom Template\';

    return $templates;
}

add_filter( \'theme_page_templates\', \'wpse_226324_page_templates\' );