[Zope] Tweaking the management interface

[peter]

I'm not a Python genious, but I do know some Python and a lot of HTML.

I would like to experiment with changing the way the management interface is
built up.
The management interface of Zope is basically built up in two-column frames
like this:
------------------
|     |          |
|     |          |
|  1  |     2    |
|     |          |
|     |          |
|     |          |
------------------

Which is in HTML code:
<frameset cols=175,*>
 <frame name=manage_menu src=http://url/manage_menu>
 <frame name=manage_main src=http://url/manage_main>
</frameset>

But I want something like this:
------------------
|     |          |
|  1  |          |
|     |     2    |
|-----|          |
|     |          |
|  3  |          |
------------------

Which is in HTML code:
<frameset cols=175,*>
 <frameset rows=150,*>
  <frame name=manage_menu src=http://url/manage_menu>
  <frame name=manage_extramenu src=http://url/manage_extramenu>
 <frame name=manage_main src=http://url/manage_main>
</frameset>

In frame 3 I want to load a DTML Method, DTML Document, Python module, .dtml
file or whatever is possible to load there.

So I can change this simply in zoperoot\lib\python\App\manage.dtml
I save a file called extramenu.dtml in the same location as menu.dtml and
main.dtml, zoperoot\lib\python\App\ and zoperoot\lib\python\Ofs respectivly.

All I get is an 'Resource not found' error in frame 3.

So, where should I save my extramenu.dtml and should at all call it
extramenu.dtml or manage_extramenu.dtml?
And do I have to change any Python code?