toolbar checkbox / dropdown

Hello,

I'm new with the CKEditor and I try to create a simple plugin that adds two new buttons into the main menu bar. I can add a default button with an icon and can execute some javascript code.
How can I add a checkbox into the toolbar like the "maximize" toggle button and how can I add a drop down menu like like the font size /style?

I use this code:

 editor.ui.addButton( 'myplugin', {
                        label   : 'my label',
                        command : 'myfunc'
                    });

I have added a item "type : 'checkbox'" but that does not work.

Thanks