Access the Custom Metrics Editor from the Group Selection Dialog
To access the Custom Metrics Editor from the Group selection dialog of a visual:
On a visual, select the group label (x-axis label) to view the Group selection dialog.
Select in the Attributes, Number or Time section of the dialog. The following menu appears:
Select Add Custom Metric to access the Custom Metrics Editor and create a custom metric.
Be sure to save the dashboard after creating or modifying your custom metric. If you close the dashboard without saving, your custom metric will not be saved.