Adding additional circles on an existing line chart

I currently have a chart as seen in the image [here](https://i.stack.imgur.com/jjwfp.png) -- it's a simple line chart with a dataset of [x: minutes since start of day, y: Int (from 1-10)].

I have additional "notes" with [x: minutes since start of day, y: String].

Using those X coordinates for each note, I want to calculate the y value on the existing line and then add a point on the chart at that x,y coordinate with a different color circle and some way to access the relevant string (i.e. I want to add the grey dot as seen [here](https://i.stack.imgur.com/kkjyr.png). When the user clicks on the grey dot, I want to be able to access the string to show it in another view)

Is this possible?