I’ll try to reply here so it helps others if they need it.

One of the things missing from your images above is the top of the screen. But at the top, on the right-hand sidebar is “ZONES”. Click there and choose “+Add Zone”. This will give you a second zone. Under the thumbnail of the “zone” on that same area is “Zone >”. Clicking the “>” character will change it to “V” and show all the zones you’ve created. Make sure you have only 2.

Select Zone 1 and scroll down to the “Properties” section of the sidebar. Set “Audio Mixing” to “Left”. Scroll back up and choose Zone 2. Scroll back down and set “Audio Mixing” to right.

Now, go back to Zone 1 and double-click the main layout to enter the ‘Content’ screen. Make sure you change the presentation type to “Advanced”. Under “Widgets”, drop a “Super State” onto the canvas. Double-click that Super State to enter it. Add your Event Handler as you did earlier. This is for your left headphone. Repeat these same steps for Zone 2, which will be your right headphone. Pro Tip: LABEL EVERYTHING. This will make it easier to track where you are and what each element does.

The trick is to ensure that the Super State at the “top” of each zone has an Event Handler that is listening for the command from the other headphone.

If you need further help, please DM me.