Overlapping bars allow comparison between two quantitative variables when both variables have comparable ranges of values.
Creating an overlapping bar chart is like creating a dual-axis chart. You must link the categorical variable to one of the axes, and the other two quantitative variables to the other axis.
Among the options specific to either of the two quantitative axes, you must check the "Dual Axis" option under "Position".
In the options of both quantitative axes, the bars must be selected as a custom mark. For each axis we choose a different color and custom bar width (we must choose a smaller width for the bar above the other one).
It is important to remember to select the "synchronize axes" option found among the axis scaling options.