You can create any group and display that group in any view. if the group contains all of the same type of device that has a turn on/off function then the group (by default) should have a control at the top to turn on or off all devices in the group.
If you mean that you still see every light within the group and you only want to see the group as one entry, you need to nest the group, i.e. put the group in another group.
An issue to consider is that when only one light in your group is on, it shows the whole group as on - you lose a little bit of granularity in the status.