You can invite contributors on both the organization setting page and the preview instance settings page.
To invite a contributor to your organization, resend an invitation, cancel an invitation, or delete a user from the organization, go to the organization settings page.
To invite a contributor to a specific preview instance, resend an invitation, cancel an invitation, or delete a user from a site, go to the preview instance settings page.
Example of contributor list:
There are three possible roles a person can have on Gatsby Preview: owner, organization contributor, site contributor. The person who created the Gatsby Preview account is the owner. An owner can invite a contributor to the organization or to a specific preview instance.
There are currently minimum permissions settings for both site and organization contributors. In the future, there will be more permissions added to the organization contributor role, and there will be more roles available.