Senders:
  aMessage -> set of methods (that send aMessage)
Implementors:
  aMessage -> set of methods (that implement aMessage)

Sendees:
  method -> set of messages (AS SENT by THAT method).

Does such a browser exist? It would be useful when browsing a particular 
method, rather than repeatedly clicking around in the code pane to 
understand more fully a method (as I do).

Selecting from the set of sent messages would either show its code (for 
self-sends, known implementor), or show a further list of its implementors 
(for non-self-sends, could be many implementors; or if you have RoelTyper or 
something fancy installed, could further narrow by type inference).

=========================================
|*method A | messgA1  |implementors of messgA2
| method B |*messgA2  |....
|          |          |....
|          |          |
=========================================
|code pane
|  self messgA1.
|  bar messgA2.
|
============================

It this an OB structure?

Sophie