Hi Jakob, the key you seek is Command+d.  It will remove all selected
methods from the browser without deleting them from the system.

I've just added that hint to the menu, I'll commit that soon.

> Use case/user story: when exploring a system, I repeatedly invoke
> senders/implementors which collects me lots of methods in such a
> browser. In order to keep an overview of the control flow I would like
> to tidy that up by removing unrelated matches (methods with equal
> names from unrelated classes).

Congratulations.  You have absolutely grok'd how MessageTrace browser
is intended to be used where I think it has been
misunderstood a lot, before.

Also, please note the role of Command+I (capital eye) to invert the
selection within the current level.  This allows you to merely swipe
the methods you wish within the indented and press two keys in
succession:  Command+I+d to leave it at just what you selected.

Best,
  Chris