How to make an expandable/collapsible category list?

This help ?
https://www.tamba2.org.uk/wordpress/kadabra.txt

Oh, you are a godsend! I’ll give it a lookover and see if I can follow it. If I can get my list looking like the one on tamba2.org.uk, I’ll be a happy camper.

If you have any problems, just post ??

I had no problems getting it to work. However, it is an all-or-nothing category list as outlined in the doc. How do I get the expand/collapse capability for each level of the category list?