Cloud accounts · Custom Google sign-in credentials
Can I use the same custom Google credentials for several Google accounts?
Short answer: Yes. The Client ID and Client Secret belong to your Google Cloud project, so you can reuse them for every Google Drive account you add. In testing mode, add each account as a test user or publish the project.
Yes. The credentials belong to your Google Cloud project, not to one Google identity, so you can paste the same Client ID and Client Secret for every Google Drive account you add.
If an account belongs to a different organisation, that organisation may require its own approval — and if the project is in testing mode, add each account's email as a test user on the consent screen, or publish the project.