I got them working for a module recently and yes, it was tricksy. I use them in Liberté for the player mats to provide a background to 5 card slots at the top of each player mat… e.g. the blue background on “Blue” player’s mat.
The player mats are implemented through Player Hands. Here are the elements involved in providing the highlighting.
The basic heirachy under the Blue player hand:
The 3 elements that set up the highlighting:
I think the tricksy bit is how you need to define two particular components - the highlight property name and its configuration and the link between the two involves two steps, zone and zoneHighlight. Brent’s post that @JoelCFC25 linked to above explains why but I haven’t tried to do anything that exploits that flexibility.