Hierarchical list

Hello,

First, thanks for this really useful plugin!

I’m going to migrate a Drupal Website to WordPress and wish to preserve the hierachical structure of a post list like Drupal’s book module.
I’m wondering, if it is possible to extend the plugin and add a parameter to the catlist shortcut that prints out the post list in hierarchical order:

[catlist post_type="post" name="Kat5" catname="yes" hierarchical="yes" duplicates="yes"]

The output should look like:

Cat5
- Cat51
-- PostA in Cat51
-- PostB in Cat51
- Cat52
-- Cat521
--- PostC in Cat521
-- Cat522
--- PostC in Cat522
--- PostD in Cat522
--- PostE in Cat522

If the HTML output of the list items contains the category names as class attribute, this list could also be formatted with a template and CSS as dropdown list.