How to limit term reference autocomplete to a certain branch in hierarchical vocabulary (D7)? I would like to add a term reference field in my user registration form, where the users should enter or select the organization they are from.

Tags vocabulary:

  - Organizations
   -- Orga1
   -- Orga2
    -- Orga3
    -- etc.
  - other parent term
  - other parent term


I think i remember, that in D6 i found a way to limit the term search to a certain branch of my vocabulary, so in this case, i was able to select "Organizations" and only the children terms where handled through the autocomplete.

I played around with various modules, but still there is no way to configure a parent term, but only set a hole vocabulary for the reference while creating the field.

Of course, i could set up a single vocabulary for the organizations only, but i fear that i will end up with a mess of single-use vocabs, while i would prefere to keep those things in one hierarchical vocabulary.

Did i miss something? Was there a change in the vocabulary-use-philosophy?
Any hints appreciated.
I use Workbench Access for this. I think you need to use the dev release, but for me, it is stable on a production site. It allows you to define which user roles and individual users can see which parts of taxonomy.