The compositions docker allows you to save the configurations of you layers being visible and invisible, allowing you to save several configurations of your layers.

Adding new compositions
You do this by setting your layers as you wish, then pressing the plus sign. If you had a word in the text-box to the left, this will be the name of your new composition.
Activating composition
Double-click the composition name to switch to that composition.
Removing compositions
The minus sign. Select a composition, and hit this button to remove it.
Updating compositions
mouseright a composition to overwrite it with the current configuration.
Rename composition
mouseright a composition to rename it.