Imagine this: I have a custom post type called 'Animals' and I have registered a taxonomy for this post type called 'Types of Animal'. 'Types of Animal' would be 'dog', 'cat' and 'mouse' and so on. So that's straightforward.
But say I want to introduce child taxonomies based on the value of the Types of Animal taxonomy. I can use the fact that the taxonomy is hierarchical but if Types of Animal contained 100 terms with 50 possible sub-terms, that makes for a big mess when I'm editing.
So what I'd like to do is display a child taxonomy, say 'Breeds', when the editor selects 'dog' in the 'Types of Animal' taxonomy.
I could use tags but I'm afraid of the margin of error inputting tags. I would rather that editors had to check a box.
Is it possible to display a child/secondary taxonomy dynamically in this way?