Steven Zahm@ Aredon
Sorry, no, I have not made any progress in seeing if I can improve the performance in the core. The only real difference I see between your custom code and the code used in the admin pages is that I use a left join to query the data in a single query rather than the two you’re using. Another difference is the core code builds the category array for n-deep child relationships; your goes just one – parent/child. I can’t know for sure until I do some real solid performance analysis but I can’t see either would be faster than the other.
I’m thinking this comes all down to the browser rendering speed and/or the time to create the HTML in PHP. What I’m doing on the admin pages is definitely “heavier” than your code.
You could verify the query times by installing Debug Bar and comparing the query times on the pages.