In excel what Sparkline formatting option creates a reference line?

In Excel, the Sparkline formatting option that creates a reference line is called "High Point" or "Low Point," depending on the context. You can also use the "Vertical Axis" option to set a specific value for the axis, which can serve as a reference line for comparison. To add these options, select the Sparkline, go to the "Design" tab, and choose the desired formatting options under "Show" group.