I wanted to have a little space between items in the 2nd ca

I wanted to have a little space between items in
the 2nd category and the next first category.  Say, if this is the tree:

Arts & Crafts

  Painting

  Drawing

  Music

Business & Finance

Cars

Gardening

How can I enlarge the vertical space between “Music” and
“Business & Finance”?

Unfortunately the
“topoffset” is only property which can control spacing between items.
You can use it to set space between “Business & Finance” and
previous item, but you can’t set different spacing based on level of previous
item.