I create a line graph, using the button to create a crosshair on the graph that follows the mouse movement.
Here I displayed in the GIF what it looks like:
https://gifyu.com/image/0kvX

I also add various graphs below and want the crosshair to capture these additional graphs.
The spaces between graphs should also be drawn with crosshair lines.
Where the cursor is located, you need to draw a vertical and horizontal line. in other cases, only draw a vertical line.
Here's the picture:
https://gifyu.com/image/0kmV

I create a crosshair using "QtChart.QLineSeries()".
The simplest thing that comes to mind is to create these two lines in each chart and hide the non-main horizontal lines.

What can you recommend?