When not using graph builder, it's easy to right click on graph and select row legend, select column, markers, alphanumeric. But I don't see how to do it with graph builder?
I can use mark by column in the datatable to mark as alphanumeric; but when this is graphed in graph builder, although the symbols in the graph are maintained as alphanumeric, the legend doesn't show the alphanumeric symbol, just the dot.