Layers Settings

Turn off Layers for non-selected Items
This option will turn of any layers which are not used by the currently selected Points/Strings/Text etc.

Turn On Layers for Selected Items
This button will tun on all layers use by Selected items (Points, Strings, text).

Sort by Layer
Tick this box to Sort the list by Layer name instead of GroupName/LayerName

Select Objects on Visible Layers Only
Tick this box to all all the Select options (point,Strings,Text) to only select items which are visible.
If this box is unticked, you can select items which are invisible (on invisible layers).
This can be dangerous if you are deleting
or editing items as you may delete or edit items you cannot see.