Drawing a line on a stacked bar chart

I want to make a reference that differentiates certain bars from others in a stacked bar chart. So either adding a line using layout shapes or creating a trace using go.Scatter, to end up with a result looking something like this.
So either the connecting line or the orange circles i drew on this chart.

the problem is: i dont know how i can reference a certain bar, such that when i change one of the bar, the line stays in the red bar (for example).

Anyone have any suggestions how i can do this?


In your app, how are you changing one bar?

In dash, the app callback returns the data (which is a list using go.Bar), and the layout (where I specify that I want the bars to be stacked, etc.)

Probably best to ask this question on #dash in this case.