Displaying Custom Field When Using the New Organization In Contact Menu
As you noted. the New Organisation is a civi Profile - and at Administer > Customise > Profiles (http://d46.demo.civicrm.org/civicrm/admin/uf/group?reset=1) you will see it on the Reserved Profiles and can therefore add your new field here and it would show assuming the 'field' is set either for organisations or 'all contact types'.