In this paper, we describe a graphical editor GRED as part of the integrated programming environment GRADE that is intended to support designing, debugging and performance tuning of messagepassing programs running on a heterogeneous network of computers. The GRED editor hides the cumbersome details of the underlying lowlevel message-passing system (which is currently the PVM system) by providing visual abstractions but allows the programmer to define local computations of the individual processes in C (or in Fortran in the future) independently from the visually supported process management and inter-process communication activities. Visual representatation of the critical (i.e. message-passing related) parts of the code can help the user in grasping the complex structure and runtime behavior of the whole parallel application, even if he or she is not an expert in the field of concurrent programming.