There is a tree view, or other grouping controls. You could try making your own control, although that may be a large effort?
Or, I've done something like this for a drop down list, although it isn't nested that you want, it may work though:
Just use spacing to move the options over.
I haven't played with 2.0 enough to have found any controls like this, other than the TreeView, or the other SiteMap controls.