Do you want to do something that the built-in row labeling won't do?
For example, open Big Class.jmp from the Sample Data directory, and do a histogram of weight. You'll not there's one outlier on the top. If you right-click on that outlier and select "Row Label", you get the name LAWRENCE, the corresponding value from the name column.
This is done by assigning the Label role to the name column (which was done already for this data table). If you want to use X and Y (of your example) as labels to column Z, select X and Y, then Cols > Label/Unlabel. From then on, in every plot, you'll have points labeled by X,Y.
But I think I am misunderstanding your question. Do you want JMP to automatically label all outliers?
Thanks for your response, I can follow your procedure to manually label points but I would like the script to do this labeling automatically for all Z values greater than a defined threshold. Is this possible using JSL?