Until version 7.2, only text fields with a dropdown list could be used as reference field. Starting with v. 7.2, you may choose a field with or without dropdown lists, including numeric and yes/no fields.
This new feature allows you to use Advanced Dropdown Lists on a series of field: Field A conditions the list of Field B which conditions the list of Field C, etc.
Reference field with dropdown list or Yes/No field
When the reference field you choose has a dropdown list, values are automatically listed in the table below. If the reference field is a Yes/No field, the Yes and No values are automatically listed.
Reference field without dropdown list
When the reference field you choose does not have a dropdown list, you need to add the potential field values yourself by clicking the Edit... button. This button only appears when the field does not have a dropdown list.
Clicking the Edit... button opens the Edit Potential Field Values window. Simply type the values, one below another.
Then click OK and the values will appear in the Edit Scheme window. You're now ready to associate a static list to the values you just added.