In PhotoFlow, there is an “hidden” tool that allows to run arbitrary g’mic commands interactively, pretty much like what is available in the gimp plug-in.
At the moment, only commands that can be split into tiles and processed in parallel are supported, but this can be changed if needed.
However, one advantage is that the results can be directly seen in the big preview area. Moreover, the custom gmic command is associated to an adjustment layer, and can therefore be combined with any other adjustment as wells with multiple custom gmic commands.
If this could be of any help in the debugging and/or development of gmic scripts, then I can easily re-enable the tool in the GUI in the next version, or even better explain which single line has to be uncommented if you will compile photoflow from source.