Combine full year data with partial year data in line chart

In a line chart we need to display the full year (12 months) for LINE A (grey line below). With that we have to plot LINE B (blue line below) but depending on what month is selected from the dropdown box, LINE B must terminate.

So far using the GRAPH.setDataSelection():

LINE_CHART.setDataSelection({"[Measure]": [LINE A, LINE B]});

This results in bringing back data for LINE A and LINE B but both for the full year.

Would you have any suggestion how to bring back full year data for LINE A values but terminate LINE B values only up to selected month (see below).

I have figured out a way that this could be done by using SDK component "Bring your own data" to populate with data separately for LINE A and LINE B, but that is a workaround resulting in disproportionate increase in scripting and drop in performance.