your request can only be done by adding a script to the graph, to generate your own text and line using JMP graphic functions. There is not an option to have the spec limit labels be displayed within the frame of the graph.
That is not a good option in my opinion. e.g in the Bivariate plot if you add label using graphic script, Y lable moves when you adjust the scale of x-axis and vice- versa. that looks very bad that label are far from the axis. I guess JMP team have to provide a real solution.