Categories hierarchical taxonomies

[gputignano]

Hierarchical taxonomies are added to a post by a tree structure and non-hierarchical one by a text field. But in same cases could be very useful to add hierarchical taxonomies using a text field, for example when I have hundreds of items or select non-hierarchical taxonomies by checkboxes or a select field. What do you think about?

[helen]

Yes, been thinking about these for the last several months and, as noted in #14877, would like to both add extra built-in metabox callbacks for taxonomies as well as making the existing ones usable for both hierarchical and nonhierarchical. I need to write up my thoughts on this as a roadmap in the near future, but I keep punting on it because we really should make the tagging interface better first. Closing as a duplicate.