Function Name Manager

Click the Function list button in the Graph Options dialog box - Custom Function (2D Graphs) or Custom Function (3D XYZ Graphs) tabs to display the Function Name Manager. Use these options to manage 2D and 3D custom functions. For example, when this dialog box is displayed from the (2D) Custom Function tab of the Graph Options dialog box, you can select a previously specified 2D function from the list.

Functions
The Functions list displays a list of currently defined functions.
Select
Click the Select button to select the currently highlighted function (in the list of functions), and close the dialog box. The content of that function will automatically be transferred to the respective edit field (for a custom function) on the dialog box or tab from which the Function Name Manager was called.
Close
Click the Close button to close this dialog box.
Edit
To edit a currently defined function, highlight the function in the Functions box, and then click the Edit button. The Edit Custom Function dialog box will be displayed, where you can modify the function. To change the name of the function, use the Rename button.
New
Click the New button to create a new function. After specifying a name for the new function in the Custom Function dialog box, you will be able to define the function in the Edit Custom Function dialog box. The new function will be added to the Functions list.
Delete
Click the Delete button to delete the currently selected function.
Rename
Click the Rename button to rename the currently selected function. The Custom Function dialog box will be displayed in which you can specify a new name for the functions.