Monochrome's sandbox: Multilevel Select

Multilevel Select adds a form element that uses ajax and multiple select element to allow quick and easy selection of values in large trees, by expanding them only one level at a time. This makes for a much friendlier user interface when dealing with large, deeply nested taxonomy trees on term reference fields.

The included Multilevel Select Taxonomy Widget module creates a widget for term reference fields that uses the Multilevel Select form element. Once you have enabled the module, edit or create a term reference field. Then select ''Multilevel select widget" from the widget drop-down box. The widget includes an option to restrict selecting only leaf terms (terms with no children).

This widget also gives the ability for the user to manually reorder multiple value term reference fields whether they are hierarchical or not, which is a feature that is useful but can't be done with core term fields.

Saving of a full lineage (all parent terms of the selected term, right to the root of the tree) of a term field can be achieved by using this module in conjunction with the taxonomy index lineage module http://drupal.org/sandbox/Monochrome/1388316

The Multilevel Select Taxonomy Widget only queries the database for one level of a taxonomy tree at a time and is suitable for use on extremely large vocabularies.

The Multilevel Select Taxonomy Widget is compatible with Conditional Fields.

Current Code Snapshot: http://drupalcode.org/sandbox/Monochrome/1388304.git/snapshot/aa880cf29c...