[plt-scheme] MrEd question about embedding editors in editors

Hi,

I have non-fixed, user-definable fields that I would like to embedd 
into some text% or a similar editor. I'm basically looking for a way to 
have trees whose nodes are labels and whose leaves are editable text 
and embedd them into a scrolling editor.

I've realized that text boxes can be inserted into an instance of class 
text%, but I'd need more: a subclass of text% that is able to embedd 
new instances of itself, to display and edit data like e.g.

Person
    Name   >Erich Rast<
    Phone  >625672<
    Adress
       Street >My Street<
       Town >my Town<
       ZIP     >the Zip<

whereas >..< fields are editable text and Person would be an object 
that can be copied, pasted, saved, extracted, including all of its 
sub-entries.

Question: Is this possible using a derivative of the text% class? If 
yes, what's the right way to do it and where can I find more 
information about that? If no, is it possible at all and do any of you 
have suggestions?

Best regards,

Erich