Google community manager, Cassie, announced in the Google Advertisers Help forums that you can now access and manage multiple merchant center accounts. Cassie said "advertisers can now access and manage multiple Merchant Center accounts from a single Google account."
In order to access a Google Merchant Center account, you must be added as a user by a Merchant Center account admin. Multiple users are able to access a single Merchant Center, and users can connect their individual Google account with multiple Merchant Center accounts as needed. Each user can be assigned different roles that provide access to various features and sections of Merchant Center.
The options include:
- Standard: Ability to sign in to Google Merchant Center and access everything in the account, except the "Users" tab.
- Admin: Standard account access, plus the ability to add, delete, or edit user roles in the "Users" tab.
For more details on how to manage these types of access rights, see this Google help document.
Forum discussion at Google Advertisers Help.
Source: Search Engine Roundtable