bug open at-Using the web asset manager from Joomla 4 could help https://issues.joomla.org/tracker/joomla-cms/43320: https://docs.joomla.org/J4.x:Web_Assets
Meanwhile-For a quick solution or test purposes, you may add your javascript in the /media/templates/administrator/atum/js/template.min.js
I will update here if it is solved but watch out for updates which might remove the content(you could do a template override then)