Method 1:
To display the value when you click on a point on the plot, click the File | Options command. On the left side of the dialog, click on the Plots option. On the right side of the dialog, check the box next to the Display value on click option.

Click OK. Now when you click and hold on a point on the plot,

the XY values will be shown in the status bar for as long as the mouse button is held.

Method 2:
You can also use the Graph Tools | Digitize | Digitize or Graph Tools | Digitize | Digitize Fixed commands to get XY values from a plot. The difference is Digitize Fixed will only let you select a point in the data, where Digitize will allow you to click anywhere on the plot. When you click on the plot, the XY values are displayed in a Grapher - Report window.

Updated August 2, 2019