Allow Custom Taxonomy Help Text Labels for All Fields

[dshanske]

In the add/edit screen for taxonomies, the fields for name, slug, parent, and description have a help text below them. For example, "Assign a parent term to create a hierarchy. The term Jazz, for example, would be the parent of Bebop and Big Band."

Suggest this be added to the Taxonomy Labels that are set when the taxonomy is registered, so you can describe how these fields are used specifically in your custom taxonomy.

This has the benefit of eliminating the special casing in edit-tags.php for category only, allowing that to be registered properly.