Adding a vertical line to QtChart displaying a QLineSeries

I have a QtChart based plot where I am displaying a QLineSeries plot. I am looking for a solution to add a full vertical scale vertical lines to the graph. (Sort of vertical markers.) I am filling the QLineseries from a "ringbuffer" so at every iteration I will need to move those vertical lines too.
So far my best idea was adding a separate QLineSeries for each line with two points with separate y but same x coordinates.

hi
you can draw a line by two points that x1  x2 is very low that looks like a vertical line