Some Z wave switches have a blue LED and some have a green LED. You could just get one of a different brand so you could tell which is on from a distance.
Another option would be to create a tiny indicator light like people used to tell if the alarm system is armed or not. You don’t connect this directly to your switch, you just have it turn on when the switch is turned on.
There are also a number of different color changing light options. Both the tiny light and color changing light alternatives are discussed in the family thread
