The error that happens there is that you lack the "<*>", it should look like this:
val list: List<Element<*>>
But I would recommend that you use the MutableList according to the documentation:
List: a generic ordered collection of elements. The methods in this interface only allow read-only access to the list; read / write access is supported through the MutableList interface.
MutableList: a generic ordered collection of elements that supports adding and removing elements.
Your list should look like this:
var myList: MutableList<Element<*>> = mutableListOf<Element<*>>()