This dialog is activated by selecting the command Non Linear Curve Fit... from the View Menu or with the Ctrl-Alt-W key. This command is always active.
This dialog is used to build a new plot by selecting the columns in the tables available in the current project. At first, you have to select the table you want to use, and then click on 'new curve' to create the curve. After that, you have to select at least one column for X and one for Y. You can also select one more column for X-errors or for Y-errors. The figure created will be a scatter plot.