This editor features JMenubar integration. The only way to edit functions is to edit its source code using something predefined as:
JMenuBar menuBar = new JMenuBar();
menuBar.add(editor.getEditMenu());
menuBar.add(editor.getFormatMenu());
menuBar.add(editor.getInsertMenu());
frame.setJMenuBar(menuBar);
You will need to use additional functions and libraries as this is just a simple HTML editor.