Q:

How should I approach wrapping the Composite pattern into the Builder pattern?

Lets say that I have a Composite set up as follows:
public abstract class Element {
    //position, size, etc.

    //element methods

    //setters/getters
}

public class SimpleElement1 extends Element {
    //...
}

public class SimpleElement2 extends Element {
   //...
}

public class CompositeElement extends Element {
     protected List<Element> childrenElements;

     //methods to add/remove/get children
}

Now, how would I go about wrapping this Composite up into a Builder pattern, so that I can simplify client code by enabling it not to care (or care less) about the intricacies of how to link children to their Composite?

A:

In your builder, add methods "startComposite" and "endComposite".  These methods push a composite onto a stack and remove a composite from the stack.  Messages to add elements always add to the top of stack.
    builder.startComposite();
        builder.simpleElement1();
        builder.simpleElement2();
    builder.endComposite();
    builder.startComposite();
        builder.simpleElement2();
    builder.endComposite();

If your builder methods always return the builder, you can eliminate the repetition of the receiver:
    builder.
        startComposite().
            simpleElement1().
            simpleElement2().
        endComposite().
        startComposite().
            simpleElement2().
        endComposite();

