I think you mean changing this variable in the file /inc/header.inc.php

define('BX_DOL_URL_ROOT', 'https://example.com/');

to:

define('BX_DOL_URL_ROOT', ((isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] == 'on') || (!empty($_SERVER['HTTP_X_FORWARDED_PROTO']) && $_SERVER['HTTP_X_FORWARDED_PROTO'] == 'https' || !empty($_SERVER['HTTP_X_FORWARDED_SSL']) && $_SERVER['HTTP_X_FORWARDED_SSL'] == 'on') ? 'https' : 'http') . '://' . (isset($_SERVER['HTTP_HOST']) ? $_SERVER['HTTP_HOST'] : 'https://example.com/') . '/');

after the instalation when this file is created, it would be the only place where it makes sense. I will try this too.