WordPress.com business hosting – file manager?

New client has signed up for business hosting with WordPress.com before hiring me to run new site.

I have installed Divi theme and now need to setup Divi child theme, as usual. Where oh where is some kind of file manager function on sites using this hosting? If I try to upload a plug for this (not my ideal choice, but I don’t see any cPanel access, either) the site won’t let me even SEE file manager plugs. Also, there are occasions where access to the WP system files is crucial, such as if site gets stuck in maintenance mode.