Optional fields can be edited in "My name" -> Administration"

on the Custom fields page

You can edit custom fields using the icons. We can Edit, Delete, and populate or modify items in the Optional field of type drop-down menu.

Type of the optional Dropdown list and Dropdown list - multiple values can be created and edited via icon:

where a list will open for you to fill in, fill in the "Name" and confirm with the "Add new" button