Running a Pi3B OctoPi .14 OctoPrint 1.3.6
It shows up under the Plugins section of the OctoPrint settings.
Upon selecting it, it shows the title "System Commands Editor" at the top of the panel and then the rest of the panel is blank.
I tried it on a Mac with Safari, FireFox, and Chrome. The latter two showed the control box but clicking on it did nothing.
I see that this problem has been around for a couple of years in the GitHub docs.
Does that plug-in work for anyone?