我没有使用此插件的经验，但看起来您可以使用名为\'wpbe_tags\':

    function template_vars_replacement( $template ) {
        $to_replace = array(
            \'blog_url\'         => get_option(\'siteurl\'),
            \'home_url\'         => get_option(\'home\'),
            \'blog_name\'        => get_option(\'blogname\'),
            \'blog_description\' => get_option(\'blogdescription\'),
            \'admin_email\'      => get_option(\'admin_email\'),
            \'date\'             => date_i18n(get_option(\'date_format\')),
            \'time\'             => date_i18n(get_option(\'time_format\'))
        );
        $to_replace = apply_filters(\'wpbe_tags\', $to_replace);

        foreach ( $to_replace as $tag => $var ) {
            $template = str_replace( \'%\' . $tag . \'%\', $var, $template );
        }

        return $template;
    }

add_filter( \'wpbe_tags\', \'wpse_99484_extra_tpl_var\' );

function wpse_99484_extra_tpl_var( $to_replace )
{
    $to_replace[\'username\'] = function_to_get_buddy_press_user();
    return $to_replace:
}