This script will print out all the properties that are changed for a Horizon Layer.
Put this script in the folder On_XSection_Horizon_Layer_Properties_Changed in your Python scripts directory.
Go to Tools->Options->Environment->Python Scripts and click "Refresh from Disk". Your script should be listed automatically.
Now, whenever the properties for a horizon layer in a XSection Window changes, the properties changed will be Python Terminal.
This simple script can be used to quickly learn which properties are being changed by user actions.