This Solution will show you how to Remove a UDV

From the Home screen select Tools → User Defined Variables

Select the "File Type" 

In the 'Name' Column, highlight the value you want to remove.

Select either the 'Backspace' or 'Delete' key to clear the field.

Saving the record will display a "Confirm" message.

 WARNING - Selecting "Yes" will remove the Variable(s) and any values they may contain, including History records. This action cannot be undone.

Below we see the screen with one less value.