A reasonably valuable use case for this functionality is for portfolio management. Using a scatterplot, 3 dimensions (x, y, bubble size) and color can be used to clearly, visually indicate which projects are highest value and move the needle the most, in an easy to understand manner. But what is often needed is also a cutoff line, a line that crosses both axes diagonally. Projects above/to the right of the line are worked, and projects to the left and below the line do not have enough added value, urgency, ROI, or whatever criteria is being used to evaluate the projectsin 2 dimensions, to be worked.
With the diagonal line, we can condense information that make take pages and pages to share in a different format, into a single, easy to understand one-page format that facilitates 15 minute reviews with C-level stakeholders, vs. hours of sometimes strained conversation to explain the portfolio status, approach and next steps.
As mentioned by Marlese, it is possible to place a static line and rotate, but that can be an endless chore of updates as the project list changes.
