multiple fittings in comparison in curve fitting toolbox

Hi everyone~

I'm using the curve fitting toolbox, for curve fitting, of course.

I couldn't figure out how to show multiple fittings in the same plot. - It seems u have to open a new window to do another fitting. I want a few fitting curves to display in the same plot. But now, when I do the second fitting, the first fitting disappears.

Any one knows about this? Let me know. Thanks a lot~