Hey Phuoc

The manual gives

PLOT LINE makes a line between the points (x1, y1) and (x2, y2). The units of x and y here are normalized screen coordinates between 0.0 and 1.0. A maximum of 1000 lines may be defined.

PLOT LABEL prints any text string on the plot starting at the coordinates (x, y). The units of x and y here are normalized screen coordinates between 0.0 and 1.0. The angle is the angle from the +x direction in degrees. The size is a scaling constant greater than 0.0 that defines the size of the font. A size of 1.0 would print at the normal font size, while a value of 1.5 would print at 50% larger than normal size. The parameter “string” may be a literal string in quotes or may be a string variable. A maximum of 100 labels may be defined.

Does that not do what you want? there is also

PLOT COMMx is used to define up to 6 comments that appear on the bottom of the plot. The parameter “string” may be a literal string in quotes or may be a string variable.

Hi Mark,

I have already done the 'plot commx' command but wanted something more easily recognizable. 

I have considered 'plot label'. I am still trying to figure out the correct coordinates for the labels but that could work.

Thank you for the suggestion.