Your app works fine, albeit it is a bit confusing how to use it. It was not clear to me that it can listen to and trigger on any notification, not just Dash button presses. So I simply had to wait until I saw the amazon dash notification before I press Save. Maybe you should make that a bit more clear.
Another pitfall I ran into is if another notification arrives while your are configuring the trigger actions. Then when you press save it will be that notification that will trigger the action!
Regarding tasker, I found that tasker can actually trigger on notifications already, so it can in fact run any task even without Dash Automation. But it doesn't remove the notification like your app does.