What permissions are needed to create an advertiser?
Advertiser user (edit access)
The correct answer is:
To create an advertiser in Search Ads 360, your Google account needs all of the following permissions:
In Search Ads 360, you need agency manager permissions.
In Campaign Manager, your user profile needs the Agency Admin role. Google accounts with multiple user profiles in Campaign Manager are not supported in Search Ads 360.If your Google account has been granted multiple user profiles in Campaign Manager, you won’t be able to create an advertiser in Search Ads 360, even if your Campaign Manager profiles have the correct roles.
Read more here: https://support.google.com/searchads/answer/2491917