I think the JSW15 is dedicated to controlling the Joker DMX interface. I use a foot controller to change scenes on an iPad running myDMX GO, but not the JSW15. The scenes can be changed using MIDI Note-On data. The MIDI Note-On data for each scene can be found on pg 26 of the current myDMX GO manual (v1.02). Most all foot controllers send Program Change data, but very few send Note information. I use a Morningstar controller, but whichever you use will need 1) a USB MIDI output jack and 2) can send MIDI Note-On messages. Once you have the controller, you'll also need an Apple Camera adapter to connect it to the iPad. Mine is an Appled branded accessory and has both a USB port and a Lighting plug for power. Once you program the controller to send the Note data for the scenes you want to map to each foot button, it works flawlessly on both the myDMX GO app and the Light Rider app. Here are some links to what I use;
https://www.morningstar.io/
https://www.apple.com/shop/pro...usb-3-camera-adapter
Hope this helps. :-)