The system provides 3 possible user-defined fields:

User-Defined Dropbox

This field will provide a drop-down box of values you can enter into the field for each item.  You'll be able to add selections to the drop-down box on-the-fly from the main window.

User-Defined Fields 1 & 2

These are regular freehand text fields, 30 characters long. 

To activate any of the fields, just type a name for the field into the space provided. (10 characters maximum.) Once named, the field will appear in the main window. The User-Defined Dropbox field will also appear in the Grid and the Filter Popup.