The File menu allows the addition to the current document of pre-defined composites. The first time a built-in composite is added a root-level 'Composites' container is created. Any subsequent addition go in the same container.
If a built-in composite is added to a document in which the default value of $NeverComposite is
true, the components of the built-in composite have $NeverComposite set to
false, ensuring the newly added composite functions correctly. If Tinderbox needs to create the 'Composites' container, it sets the OnAdd action to
$NeverComposite=false to ensure any user-created composites function correctly when added there.
The built-in composite types are: