Applying To Layers

Depending on the type of expression you have selected it will change how it's applied to the property or properties.

Selection

An expression library item that contains a single expression or multple expressions.

When applying an expression library item that contains either a single expression or multiple, it will try to find if any of the properties exist on the selected layer. If they do not exist it will try to create the property needed for the expression.

Creating a property for the expression

Sometimes you will apply an expression to a layer that does actually have the property needed for the expression. In cases like this it will try and add the properties needed to the selected layer / layers. If the property can not be added for one reason or another it will not apply the expression.