would be great if the reference line would compute averages and dynamically change, ala tableau and microstrategy..
You can actually use a calculated measure in the analytics pane by 1) charting your measure in the chart's values, 2) adding it as a line in the analytics pane (as Min/Max/Average, since Constant accepts only hard-coded numbers), 3) styling it to your liking, and 4) moving the measure to tooltips. This is however very clunky and almost impossible to discover if you don't know that's possible. Instead, the Analytics pane should let us pick any measure (doesn't need to be in the chart's fields) similarly to how the new expression-based formatting works.
