I'm still curious if any GNU/Linux wizards know why the original method was not working. Either way it is working now.
Because runcommand needs a terminal to show the launch menu, launching ES directly would break this. On Debian and friends, you can use x-terminal-emulator as the terminal starting command, which would be expanded to one of the installed terminal emulators.
@alphabetapie I feel like I responded to your question in my previous post.
Somewhat. But the inputs in the config file are not clear that they represent both the keyboard commands (which I don't want), and the controller commands (which I do want). So I had to do some experimenting to sort that out on my own.
But also, in doing that, it seems I found a much simpler way than searching the input_disk_next_btn line in the config file and adding the button command manually. Would it not have been easier to just use this menu and set the button presses here on the controller? It's an option that does exactly what I want. Just hidden in the hotkey menu.
Here is what I mean below (and where some of the confusion comes from I think). At any rate, mission accomplished.