You can set different states for your components or groups on this panel. Different component states can also have different property settings.
Click on "Show/Hide state panel" (on the top toolbar) to show or close the panel.
Click on "+" (in the upper right corner) to choose a state from the drop-down list.
Please note that you cannot choose more than two of them at a time.
Apart from the Normal state, you can delete the other states. There are also options to rename or clone them.