OK, it is not complete, but the next example seems to be just fine.
<vbox> <tree> <label>Device |Directory |File </label> <item>Hard drive |/usr/ |letter.tex </item> <item>Hard drive |/etc/ |inittab </item> <item>Hard drive |/etc/ |fstab </item> <item>Network |alpha:/home |quota.user </item> <item>Network |alpha:/home |quota.group </item> <item>Network |beta:/home/pipas |tmp </item> <item>Network |beta:/home/pipas |latexfiles </item> <item>Network |beta:/home/pipas |book </item> <item>Network |beta:/home/pipas |bin </item> <item>Network |beta:/home/pipas |documentation </item> </tree> <button ok></button> </vbox>