The History panel tracks and allows switching to previous visualizations. It also allows you to save your favorite visualizations to easily come back to them. The panel is composed of two tabs: All and Favorite.
The default tab, All, is a list that shows your previous visualizations during a session. The icon on the left shows the plot type of the visualizations. The title on the right shows what changes have been applied in that visualization. Hovering over a history entry will display a tooltip indicating exactly which features were mapped to each dimension in that visualization.
Selecting any history entry will immediately switch to that visualization. Selecting the Star icon on the right of any history entry will save that visualization in a separate list on the Favorite tab.
The Favorite tab shows all visualizations that were starred in the All tab. This list functions identically to the All tab, except that clicking the Star icon will now remove that entry from this list.
Adding visualizations to the Favorite list then saving a .vip project file is a good way to save visualizations for later review. You can also rename history entries by right-clicking and typing a more descriptive name for the visualization.