Reference elements with continuous x-axis enhancement

At the moment, you can pick a continuous x-axis for reference elements and use Category-by configuration (using "Parent axis expression" option) to have the exact calculation for each value on the x-axis (not one level of aggregation for all points).

This type of behavior is not covering one usecase: What if you want to have reference elements (e.g. band) to be based on some specific formula dependent on x-axis (simply have some predefined area where points will be plotted on top of that, the area is defined upfront by some shape). At the moment, you can put formula at reference element Value. But the range as well as connected points for this reference element, are only in place where the data points are present, this means that the shape on the screen is changing based on data points available (if I have 2 points, the band border will be simply straight line connection, no matter what function is filled down). So, the behavior where reference element should be based on the exact formula. See in the attachment the situation of the reference element (red) and the line (done as "lines and curves"). We can see they are not aligning as reference elements are not calculating the expression for each point.

I would like to suggest to have option to do this band based on curve and not depending on the points that are in the data - this should be an additional option to the current feature.