External GIMP editor for RT 5.4 in Linux Mint

I have been running RT 5.4 in Win7 but finding it to be quite slow on my PC. When switching between file directories it often fails to respond for a time. My image files are stored on a 1000GB WD passport connected via USB.

However I have now installed both RT 5.4 and Gimp 2.10.4 on a second HDD which is running Linux Mint 18.
In this setup I find that RT is impressively fast compared to Win7.

I need some help now with assigning Gimp as the external editor in the RT Preferences panel.
I assume that the required custom command has to be a Linux command that will open Gimp and load the tiff image displayed in the RT preview window.

My knowledge of Linux commands is almost zilch. Whatever I do just responds with a notice to say that the path I entered is incorrect. Does anyone know the correct string of this command line?


Thanks for responding.
In fact I’d already spent some time looking at that rawpedia info.
The closest approach I could get to the command line in RT preferences was the following:-

“/usr/bin/flatpak run --branch=stable --arch=x86_64 --command=gimp-2.10 --file-forwarding org.gimp.GIMP --remote”

For a fraction of a second it opened and closed Gimp only to display a bug report which I will have to forward.

See the screenshot