Well... It's time to assume the therapeutical values of this
forum in my particular case : ) One more time, just after recurring
to all posiible ways to solve it, and afterwards posting a topic
here, I change my approach and find the solution...
In this case it is required to cast the return of all the
getChildAt() in the nesting structure, except the last one.
You can access a nested child to add a new child to it's
display list as follows:
Accessing a deeply nested child's name property looks as