CKEDITOR 4如何定义折叠和非折叠按钮组？

config.toolbarGroups = [
    { name: 'document', groups: [ 'mode', 'document', 'doctools' ] },
    { name: 'clipboard', groups: [ 'clipboard', 'undo' ] },
    { name: 'editing', groups: [ 'find', 'selection', 'spellchecker' ] },
    { name: 'forms' },
    { name: 'basicstyles', groups: [ 'basicstyles', 'cleanup' ] },
    { name: 'paragraph', groups: [ 'list', 'indent', 'blocks', 'align', 'bidi' ] },
    { name: 'links' },
    { name: 'insert' },
    { name: 'styles' },
    { name: 'colors' },
    { name: 'tools' },
    { name: 'others' },
    { name: 'fold' } // 新增的按钮组
];

config.removeButtons = 'Cut,Copy,Paste,Undo,Redo,Anchor,Underline,Strike,Subscript,Superscript';
config.addButtonsToGroup('fold', 'Bold,Italic,Underline'); // 将Bold、Italic和Underline按钮添加到"fold"按钮组中

CKEDITOR.replace('editor', {
    toolbar: 'fold' // 使用刚刚定义的"fold"按钮组
});