FileBird has a unique setting option which allows each WordPress user roles to have access to folders created by each one of them alone. So, for instance, if a user with an "author" role is logged in to the website's backend and then creates folders in the gallery, he alone have access to that folder, similarly, the same condition applies for other user roles as long as they have access to the website's backend.
However, this setting is only set to work with all the normal WordPress user roles, so any customized role functions using third party plugins may not work.
You only need to turn ON this option under WordPress Settings => FileBird. See gif image reference below: