By
linking the manager account to the AdWords accounts, it will streamline the app review process and reduce the number of times you need to go through the authentication process to manage the AdWords accounts through the API. Calls made with the credentials of a manager account can target the manager account and all the accounts that are beneath it in the hierarchy.
A Developer token can be used to target
any AdWords account, by using the OAuth2 credentials of the target account or one of its managers. You need to generate refresh tokens by logging in as a current user of the targeted account or one of its manager accounts to authorize the request and persist these refresh tokens in your application. You may then be able to use your existing developer token to target the AdWords accounts using AdWords API. Let me know if you have any other questions.
Bharani, AdWords API Team.