New option '(Everyone)' has been added to 'Assigned usergroups'. When it is selected, every user has privileges as if he is the 'assigned to' user of the item. Also, when a usergoup is added to the workspace, it is automatically taken into account. 

Scriptwriter can use API to set 'Everyone' (case insensitive) as 'Assigned usergroup' value for Item. Also, 'Everyone' can be used in the API ItemFilter as criteria for filtering items. E.g. criteria AssignedUsergroupIds = "everyone,3" will return items where AssignedUsergroup is '(Everyone)' or its id is 3.

'(Everyone)' is also available in the itembox filtering.