I have added a line to a graph at a specific place on the X-axis. Using the Programming Control dialog, I have set the attachment to "Layer and Scales". Using the Object Properties dialog, I have set the alignment to "Vertical" and "Whole Layer". I also set Coordinates to "Units: Scale" and the "Begin" and "End" X-axis to 723/723 respectively.
My goal is for the line to stay at that X-axis point and stretch vertically when I scale in and out of the graph. I HAVE DONE THAT.
However, I also want to attach some sort of label to that line (see image) such that the label is attached at the top of the stretched line and stays there (remain visible) when I scale in and out of the graph.
I added a Text object (meant to label the line) to the graph and tried every combination of settings and cannot get the text to stay aligned with the line and remain visible.
As you have ver 9.0, you can also try the menu item: Graph->Add Straight Line which will allow adding a vertical or horizontal line at a specified location and provides a label that goes with the line, which can be locked or left editable.