Calendar:Server Calendar Groups
Similar to subscriptions, servers also supports groups of calendars that exist on the same server. Groups can be invited to a meeting or all calendars in a group can be viewed in parallel, which can help to find an initial time slot for a meeting.
Required UI changes
Display and modification of those groups should be possible in an own dialog. Address book support is required to extend the group by new calendars.
A mock-up of a dialog that enables group editing will be posted here.
Optional UI changes
A group calendar is the union of all calendars in this group so it would require a hierarchy in the list of calendars that can be displayed with a single click.