Help to add grand average line in line chart in Power BI

[RobertoMonzon]

I have a table with three columns: "Workers" where I have the names of my employees, "Stage" where I have the names of the stages where the work process goes, and finally, I have the "Duration" column, which is the time it takes for an employee to complete that stage.

I created a line chart with "Stage" on the X-axis, the average "Duration" on the Y-axis, and "Workers" in the Legend. My chart works as I want it to; it creates points if the worker stays only in that stage where they started, and it creates a line to move to the next stage.

My problem is that I want to create a secondary line to represent the overall average, but it seems impossible. I don't know what to do, and I hope someone can help me.

This is how it looks

And this is how it supposes to look

The white dotted line represents the general average per stage, but I made it by making another line graph behind the original and removing the legend. The problem is that it is only a visual effect and eventually when my column has more stages and I have to move with the scroll bar to the right I will not be able to move the graph that is behind

Help me please

[lbendlin]

One way to do that would be to add a fake worker named "Average" to your source data in Power Query or in a calculated table in Power BI.  That would only work if the chart doesn't need to be interactive.