This is a very clever method and I can't wait to try it out. I followed your isntructions and have the python script saved inside the scripts directory. I ran Cura 4.8, sliced a cyliner, clicked on Extensions > Post Processing > Modify Gcode and clicked on add script. GradientInfill was not there. Restarted Cura. Same result. Rebooted everything. Same thing or did I mess up somewhere?