in the current dashboard filter, it is possible to display selected groups only. would be useful to provide the opposite - excluding host groups.

in the most simple case it could be another choice in the dropdown, although for extra flexibility another selectbox might be needed - for example, if hosts H1 and H2 are in groups GA and GB, but host H3 is only in GA, we could include GA and exclude GB, thus only seeing host H3

Specification: http://www.zabbix.org/wiki/Docs/specs/ZBXNEXT-1399