A layer's Multi-Light attributes
The Multi-Light section lets you render different lighting elements at once for a certain layer. Selecting one or more lighting elements in the UI will produce as many additional outputs for the currently selected layer. Each output will only contain the light emitted from the selected lighting element. This powerful feature lets you then composite lighting elements in comp or mix them using i-display. Refer to Multi-Light Rendering for more.
Display All Light
This toggle is only useful when using light groups. By default, if a light is present in a light group, it is not shown in the Lights section of the UI. This is the correct behaviour because it is incorrect to composite lighting elements which have light sources repeated. If you still wish to see every light source, even if it is already included in some light group, toggle this option on.
Refresh
This button lets you refresh the Light and Groups list in case you added, removed or renamed some light sources.