Hi Tomek,
Thank you for your question.
This should be possible and allow me to discuss how you can implement this.
Firstly, you will need to identify a user/email address that can be given
access to each of the client accounts outside your MCC/manager account's hierarchy. Once the said access has been provided, you can then use that user/email address to generate its own set of
OAuth2 credentials.
Once the credentials have been generated, you may then use those to authenticate your API requests when accessing any of those client accounts.
If you prefer to use different users/email addresses for each of the client accounts, you can provide access to each of those users/email addresses separately for each of the client accounts. This way, their respective OAuth2 credentials can only be used to authenticate API requests for the client accounts they are associated to.
I hope this helps and let me know how this goes on your end.
Best regards,