Adding properties to a sub component’s UDA in a custom component from the main component

Question:
How to add a property to a custom component so that the property appears in the User-defined fields of the sub component parts?

Answer:
You have to activate the User-defined field by entering a value into the field. After this you can use the field in the Component Editor.

See also a detailed description of the process here: Example of a variable formula: Link variables to user-defined attributes.