While FoxyCart has had the ability to share stores across users from day 1, we never got around to building an interface to allow our users to add or remove users directly. We finally had somebody explain that this put a serious kink in their project workflows, so we added some functionality in the admin of v060 to grant and revoke store access.
The screenshot shows this new functionality in action. At this point FoxyCart still doesn’t support more fine-grained access controls, though it is something on our request board. Any admin user can add additional users to a store. If an existing admin user is found with the entered email address, access will be added immediately. If an existing user isn’t found, one will be created with a temporary password. And email notifications of access changes are sent to all admins with store access, to ensure that everybody is on the same page.
We hope that this will save you some hassle as you serve your clients. Again, this is only available in the admin for stores on v060+. Please let us know how you find this functionality in our forum.