add_tag_form_pre
Action Hook (deprecated): Fires before the Add Tag form.
Source: wp-admin/edit-tags.php:407
{$taxonomy}_pre_add_form
Action Hook: Fires before the Add Term form for all taxonomies.
Source: wp-admin/edit-tags.php:424
{$taxonomy}_term_new_form_tag
Action Hook: Fires inside the Add Tag form tag.
Source: wp-admin/edit-tags.php:443
taxonomy_parent_dropdown_args
Filter Hook: Filters the taxonomy parent drop-down on the Edit Term page.
Source: wp-admin/edit-tags.php:497