Integrate-Gadget
The Integrate Gadget performs numerical integration on a data plot to calculate the area under the curve. You can select an arbitrary range of the data plot using the region of interest (ROI) object overlaid on the plot.
Some gadgets operate on a single curve at a time, but you can repeat your analysis for other curves by clicking on the fly-out menu and choosing New Output for All Curves or New Output for All Layers.