Light Source Groups
Light sources can be grouped together to help organize the list of light sources. Light source groups also allow you to enable or disable all of the light sources within the group with a single click by clicking on the Enabled column next to the group in the list of light sources.
Create a new group by clicking on the 
New group button.
To place a new light inside this group, click on the group on the list, then click on the New light 
button.
To place an existing light inside this group, select the light you want to move by clicking on it in the list. Drag and drop it on the group where you would like to place it.
Groups of light sources may also contain other groups.