I think right now this hasn't been offered yet. Is there other way to achieve?

Just like combotree,if we can see the checkboxes ,it will be much clearer when users choose.

In combotree,the Property 'onlyLeafCheck' works when I set 'multiple : true, checkbox : true', hope it works too when I set ''multiple : false, checkbox : true', i.e. single select.

Another question , in datagrid we have the handler onSortColumn now . But I couldn't stop the sort action by it.Hope give some tip. Many thanks!