I have to make an application for eeg data visualization.

This post contain an example of what I want: https://forum.qt.io/topic/107467/plot-eeg-samples

As you can see, each graph share the x axis, and has its own "0" on the y axis. Each y axis are equally separated, and the graphs can overlap each other.

Right now, I'm able to display all the graph (they have transparent background) in a vertical layout, but I can't find a way to make them overlap.
I'm using QCustomPlot, with each plot containing only one graph. I tried putting all the graphs in only one plot and creating multiple y axis, but the problem is the same, with each plot one below the other...

Do you have any suggestion ? Maybe placing the widget by using coordinates instead of layout ? But it seems prone to errors as I have a variable number of graph...