With the Double drop-down it is possible to add a two-level selection, letting you set multiple sub-choices for each primary choice.

For example, if the choices list different countries, sub-choices could list cities in each country. 

• Mark the desired Field ID in the Field Tree. 

• Select Double drop-down in the Data entry field.

• Fill in the primary choices in the inline table.

• For each primary choice, enter the table editor and add sub choices.

  

• A new table for sub alternatives appear. Fill the table and click back when complete.

• Instead of a text field in the Fill In Form, the field now contains two drop-down lists: the main choices, which in this case is a list of countries, and sub-choices, with corresponding cities.