Field States UI no longer works with the Taxonomy Term Reference Tree module → . It used to work beautifully for hiding long hierarchical lists of taxonomy terms, and making them visible only when conditionally needed. The term_reference_tree widget is great for these types of select lists.
DB error log: "Field type: "entity_reference" with widget "term_reference_tree" was unrecognized.
Install term_reference_tree and use it as the field's widget.
Add support for the term_reference_tree widget.
Active
3.0
Code