Have you tried creating a Reference line? (Right click on the Y axis and choose "Add reference line...") That might work if those variables aren't changing.
I created a calculated field called Target.
IF ATTR(Time)="Plan15" THEN [Modified] END
This isolates your goal.
I then added Target to the Detail shelf in your view.
Right-click on the y-axis and select add reference line.
I then selected Target as the reference measure.
This generates the correct reference line
Testing_External Revised.twbx 24.4 KB
Thank you so much!! this is perfect.