While only today I've have a feedback from a macOS user you need to install this or this updated version.
I'm sorry for the inconvenience.
It have to look something like this:
@Keet & not only
On the right last row I've insert information's related to the next level(if exist).
At start, the plugin verify this and set the calculated thickness.
Modifying the steps number, the next level indicator will warn you.
When next level: 0 cm you have to be sure the last tread it is at the same elevation as upper room.
Try with the test file I've provided.