How to allow visibility to En route button only on specific activities in route?

Summary:

Is there a specific property or process that can be used to restrict visibility to the En route button if the task is not next in a tech's route? Basically, we only want it visible in the following situations:

Next task in route, when previous task has been put in completed or suspended/not done statuses

Not ordered activities

non-scheduled activities

Since the position of the next task in route changes throughout the day, simply using position in route isn't working. I need to understand how to overcome this when configuring visibility to the En route button on technicians' profiles.