On the Windows platform one can assign the associated program with the help of the ooDialog program "%REXX_HOME%\samples\oodialog\ftyperex.rex".
This program would allow for associating Rexx programs with the IBM workbench, which is not available in the opensource version of Object Rexx. Therefore this choice needs to be removed.
Also, the new path to the exe-file misses a quote right before the name of the exe-file causing hangs of the session in which a Rexx program would be started thereafter. Starting such programs via the explorer would bring up a popup with a list of programs to use to process the Rexx program.