Vala GTK3 find child by name - gtk3

Question

Using Vala 0.30, how do you find a GTK child widget by name?
The main code calls a function to set up the application layout:
text.application_layout ();
The function creates the window and layout boxes.
class Example : Gtk.Window
{
public void application_layout ()
I want unrelated code to place content in some of the boxes. In C + GTK I could define the window as a global variable and any code could find a child box then add content. I cannot find a working equivalent in Vala.
Jen suggested using Container.get_children(). I will experiment with that. In the previous C code, the get_children approach produced thousands of children when a grid was populated.
Some Web pages show Vala classes with public strings. Vala will not compile the examples of a class when the public variable is a GTK widget. I also tried a dozen variations that work in other languages and fail in Vala.
Finally I found a way to have a public GTK widget that can be found by other code. The following compiles. All the online examples are slightly different and fail to compile in the current Vala.
class Example : Gtk.Window
{
public Grid example_grid = new Grid ();
public void application_layout ()
If this is the only option, I will have to make many items public public.
I will still have the problem of finding the last child in a variable length set of children, something like the last label added to a box or the last row added to a grid. I would like to label items in a long list with a name like last then find it direct instead of reading through a thousand children every time.
Another update. The following grid definition works from within the class. It works from other methods of the class when called within the class.
class Example : Gtk.Window
{
public Grid example_grid;
this.directory_grid = new Grid ();
My main code has var example = new Example(); and passes the example object to other code that needs user interface elements. The other code can then access example.example_grid or a method that updates example.grid. This means changing the other code to accept the example object.
I found then lost a page showing how you can access the main window object without having the object passed to the function. If I can find that again, it would let me access example.example_grid without having to change the code to pass the example object. This is getting close to a solution.