docConsult Support 

Authentication details are encrypted and stored here: C:\Users\username\AppData\Roaming\Trados\Trados Studio\Studiox
In a file called: TranslationProviderCredentialStore.bin

So while you may have it listed as a template resource, the user in question must have:

• DeepL plugin installed
• Authentication at user level

If DeepL has something like Client ID and Secret as we do for Language Weaver, we would be pleased to implement this as its a way of supporting automatic systematic workflows.

Lyds

Thank you Lydia Simplicio. We are indeed trying to create an automated workflow but since Studio is running under a managed service account, we cannot enter the API key (thus creating the .bin file) in a conventional way. Is there perhaps a workaround?

DeepL do offer SSO options, although only for their Advanced and Ultimate team subscriptions:
support.deepl.com/.../11851068625052-Single-Sign-On-SSO

docConsult Support seems we are both stuck if I read your update correctly, given you are not using Advanced or Ultimate. I will happily log an investigation with regards to alternative authentication methods to support your use case, but for now I would not have a workaround. 

They way I see it, the instance of Studio that is doing the bulk of the pre-translation needs to be authenticated and as an exception have means to access the .bin files.
Language Cloud supports DeepL, perhaps use that to manage your initial project processing, then bring the project into Studio?

Lyds