Hello @Rwe,
Please post your question in the official support thread for this contribution:
Your question is also not specific for this add-on. It is about all header modules.
The header modules can't be placed before the navbar in a standard store because the order of the content groups is defined in template_top.php and header.php
However you could create a new group which contains only the holiday message module and place it before the navbar.
Have a look in template_top.php and header.php to see how it is made.
You would need to add the call for the new group ("before_navbar" is just an example, you can call it as you wish) :
<?php echo $oscTemplate->getContent('before_navbar'); ?>
in template_top.php before:
<?php echo $oscTemplate->getContent('navigation'); ?>
Then create a directory called "before_navbar" in includes/modules/content/
Then you would need to move the holiday module into this directory and change the coding in the holiday message module to fit the class name etc.