Note: not available in all versions.
When a field is marked to use presets the user will only be able to select from a predefined list of entries. This feature is used to establish this preset list of entries. Only alphanumeric and numeric fields can have presets. Date, Time, Timestamp and Counter fields are precluded.
If you select a field to use presets and no entries have been put in the associated list, then a dialog will open to allow you to enter them. If entries already exist they can be modified by pressing the associated Set button. In either case a dialog like this will appear:

Enter new selections in the top field and press the Add button. To delete an entry, select it in the list and press the Delete button. All entries can be deleted by pressing the Delete All button.
The entries are stored and displayed in alphabetical order. If you are making preset entries for a numeric field, you will only be able to enter appropriate numbers and possibly a decimal point.
If you wish to permit an empty selection as a data entry, enter a single space for one of the entries.
Note that if you make changes to the list and press the OK button, they will be made even if you press Cancel on the subsequent dialog.