The Unbabel Admin of a Unbabel for Freshdesk installation is simply the user through which the authentication between the two instances is performed. We use their api key to read and deliver content to the tickets.
If you need to change the Unbabel Admin, all that is required is that the new user taking on the position is assigned an admin role - see how to do that in this article - and the Access Token under the Settings Page is changed as to match that user's API Key.
We highly recommend that you double check that the changes are saved by reloading the page. Having the access token matching the Unbabel Admin's API key is fundamental to ensure the translation flow remains functional.