When under: Monitoring -> Screens, adding a "Host Group Issues" element and setting the "Host Group" field to be a parent group of several nested groups, the "Host Group Issues" dialog will not display issues or status of any host belonging to a nested host group within the parent.

For example, given the host groups:

Servers
Servers/Chicago
Servers/Dallas

If you select Servers as the Host Group, nothing within Chicago or Dallas will be included.

This also applies to the Trigger Info element as well as possible others.

This would be a very useful feature for being able to create screens that list a general overview of an entire group of nested groups.