This article will teach you how to establish a new custom field with a multilevel option. 

The first step is to add a new custom field. Go to Listivo Panel -> Custom Fields -> Add New Field.

Write down Your field name and set the type as Taxonomy. Only this field type allows selecting the multilevel option.

Find your new field on the custom fields list and edit it.

Set check-box Multilevel. Options Search logic will be permanently set for "and" and Allow Multiple Values will be checked - those options are required and will be set automatically.

Example:

The category field is set as Multilevel. Users can to choose the category Electronics and then select a subcategory (like computers).

The category field isn't set as Multilevel. Users can to choose the category Electronics and then is no other options.