Yeah, this is more of an interpreter request, not GUI.

I'm afraid not. After doing 'debug_on_error(true)', when an error is raised inside a try/catch block like this:

try
   ... some code ...
   ... error() happens in a function call in here ...
   ... some more code ...
catch err
   error('Something bad happened: %s', err.message);
end

the breakpoint is hit at the error() inside the catch block, not the original error. This seems like the same behavior as plain "dbstop if error", not "dbstop if all error".

Matlab has a convenient "dbstop if all error" command that allows you to set a breakpoint that triggers whenever an error is raised, even if that error is inside a try/catch block. This lets you get right to the original cause of an error when it happens deep inside a call stack with multiple try/catch blocks.

It would be nice if Octave could add support for this.

I see a similar (unimplemented) "dbstop if caught error" in the "dbstop" documentation, but I think this would be a bit different.