List View (Dropdown) with submenues for Unity 3D

I need a programmer for a List View (Dropdown) with submenues for Unity 3D with the following specifications:

- Dropdown with submenues
- Adding new items
- name an rename items
- checkboxes for activate/deactive each item
- change the order o f the items via drag and drop

One more detail: We'd also have to be able to initialize the menu content and status from code and also read out the content and status of a given dropdown. Like having the name, order and active/inactive status of the items in a list be readable from (to set up a list) and saveable to (for later use) a json string. So we're not working with static menus that are only set up once in the editor.