Not sure if this is even possible with current 5.5 studio interface .. however I was able to hack the saved html of a regular scatter chart to add an "identity line", so HighCharts certainly supports it. Imagine a dataset the has two cost items per row and I'm xy plotting one cost against the other. What I also want to show is an "identity line" from 0,0 to MAX(maxXCost,maxYCost),MAX(maxXCost,maxYCost). From wikipedia: “A scatter plot is also very useful when we wish to see how two comparable data sets agree with each other. In this case, an identity line, i.e., a y=x line, or an 1:1 line, is often drawn as a reference. The more the two data sets agree, the more the scatters tend to concentrate in the vicinity of the identity line; if the two data sets are numerically identical, the scatters fall on the identity line exactly.” Anyone happen to have done this and can provide an example? .. or maybe you can outline how to do it? Thanks