When creating a new Task, the Subject field has an icon to the right that allows you to select from a pick list... yet it is not required that you use one of the defined options. It is the only Pick List field in Zoho that is set this way. In the Field Customization Area for Tasks, you can add different options to the Pick List, but there is no other indication of how to replicate this field implementation.
Would be GREAT to add that capability to other Pick List fields, where there were suggested options, but entries are not required to be on the list.
Susan