Balance history shows your historical balance on each account. You can also see the Net Balance of all selected accounts by using the Net Balance button at the bottom left. To access the graph go to the web dashboard - 'More' - 'Balance History'.
Incoming vs Outgoing Graph
You can modify the In: Out view using the group/tag selectors below the graph and the Change Account button. To view historical pie chart by group and transactions select a month and click on the vertical bar.