A project can be assigned to a user who has access to the account. This makes it easy to track who is responsible for the project and gives you the option to only grant access to projects where the user has been designated as responsible.

To assign a project, when creating or updating the project, click on 'More options' and select the user's name.

If the user only needs access to assigned projects, you can set the permissions to "Own projects" via 'Access Management'.