Label Class is a property of the Attribute class (and its descendants) in the Theme object.
It allows establishing the class that will be assigned to the label of any attribute or variable in the Abstract Layout.
Given an attribute or variable in the Abstract form that is associated with a class (Attribute), its label will take the settings of the class specified in the Label Class property of the Attribute class. The Label Class property is always associated with a Textblock class or any descendant of it.
Consider the following example where the variable on the form is associated to the "Testvar" class.
In the Theme, the Label Class property of the "Testvar" class is assigned to the "MyLabel" class.
"MyLabel" class is a descendant of the Textblock predefined class.
At runtime, the variable label will be associated with the "MyLabel" class.
As from GeneXus X Evolution 3 Upgrade 4.
Label caption property