private ArchiveNode getProgramArchiveNode() {
		GTreeNode rootNode = getGTree().getModelRoot();
		List<GTreeNode> children = rootNode.getChildren();
		for (GTreeNode node : children) {
			ArchiveNode archiveNode = (ArchiveNode) node;
			Archive archive = archiveNode.getArchive();
			if (archive instanceof ProgramArchive) {
				return archiveNode;
			}
		}
		return null;
	}
This creates all the actions for opening/creating data type archives.
It also creates the action for refreshing the built-in data types
from the class path.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/datamgr/DataTypesProvider.java