Bug 37353 add variable button can't add variable only edit. [build path}
Project->properties->java build path->Library tab->add variable button will only allow you to extend or edit a variable not add a variable. The only way to add a classpath variable is to go Window->preferences->java->classpath variables->new button.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/NewVariableEntryDialog.java
}
	}
	
	private IPath[] chooseExtensions(CPVariableElement elem) {
		File file= elem.getPath().toFile();
		JARFileSelectionDialog dialog= new JARFileSelectionDialog(getShell(), true, false);
		dialog.setTitle(NewWizardMessages.getString("NewVariableEntryDialog.ExtensionDialog.title")); 
		dialog.setMessage(NewWizardMessages.getFormattedString("NewVariableEntryDialog.ExtensionDialog.description", elem.getName())); 
		dialog.setInput(file);
		if (dialog.open() == Window.OK) {
			Object[] selected= dialog.getResult();
			IPath[] paths= new IPath[selected.length];
			for (int i= 0; i < selected.length; i++) {
				IPath filePath= new Path(((File) selected[i]).getPath());
				IPath resPath=  new Path(elem.getName());
				for (int k= elem.getPath().segmentCount(); k < filePath.segmentCount(); k++) {
					resPath= resPath.append(filePath.segment(k));
				}
				paths[i]= resPath;
			}
			return paths;
		}
		return null;
	}
	
	protected void extendButtonPressed() {
		List selected= fVariablesList.getSelectedElements();
		if (selected.size() == 1) {
			IPath[] extendedPaths= chooseExtensions((CPVariableElement) selected.get(0));
			if (extendedPaths != null) {