Existing events are automatically migrated to the new permission concept when updating to version 3.0. The defined space link is taken over, so that existing events still are only visible for members of the configured space after the update.

The editor permissions for existing events may have to be checked or adjusted, since only the event creator and Confluence administrators will have editor permissions after the update.

The event may then no longer be visible if the deleted space was the only linked space of the event. If the visibility was restricted to more than one space, it can no longer be edited. To repair the event, a database administrator must empty the table 'AO_E4409B_EVENT_SPACE_KEY' for the affected event.

An automatic migration of all editors is not possible. Please verify that everyone who managed your events before is now entered as an editor in every relevant event.

Due to the changes to the permissions model, it can happen that some former editors now can't see certain events due to visibility limitations. That's why those people need to be entered as editors individually.

By default, the event creator and all Confluence administrators can fully manage an event.

You can enter additional editors in the create/edit wizard. Editors you enter this way receive the full control over the event, just as the creator and the Confluence admins.

No, you can't do that.

You can only enter spaces which you can see. If you don't have view permissions for certain spaces, you also won't see them in the list during event creation.