To drill-down to the next sub-category, click on a desired column to perform the drill action. 
Drill Up
To go back one level, click anywhere on the chart and drag up until you see drill-up animation. You can also drill-up by using the Zoom-out button on the toolbar of the visual.
Go back
Use the "Back" button on the toolbar (top-left corner by default), which will undo the last interaction with the chart.
Finetune zoom
You may finetune your chart appearance by dragging up/down and left/right. Dragging it up will zoom in. Dragging it down will zoom out. Left or right drag will move x-axis to left or right revealing more data. Click on the chart and drag to any direction. You may use dedicated "left" and/or "right" buttons which become visible if there is more data available in the particular direction.
Toggle Lin/Log view
Toggle y-axis from linear to logarithmic scale and back. Use dedicated "Lin/Log" button.
Select a column
By default a column will be selected with a click if there is no more drill-down available. If there is drill-down available, clicking on a column will invoke drill-down. 
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Multiple Select
 Ctrl + Click to select multiple columns.
Hide/Show series
Click on a legend (if legend is enabled) to toggle visibility of a particular series.
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