Available in version 53 and later.
SetUnitProperty(<-unitUID <-propertyName <-propertyValue)
For a unit, set the value of a specified property. If a partUID is used, then the parent unit will be used.
Property names are strings. You can see a list of property tags here:
https://knucklecracker.com/wiki/doku.php?id=ixe:json:start