Click the Add to list button on the Custom Function tab of the 2D Custom Function Plots dialog to display the New Style dialog, which is used to specify a name for the function you want to add to the function list.
Style name. Type a name for the new function in this field.
OK. Click OK once you have specified a name for the function. You will then be able to define the function using the options on the Custom Function tab.
Cancel. Click Cancel to exit the dialog without specifying a name (or creating a new function/style).