To disable a menu item, set the 'disabled' property to true.
tools:[{
id:'btn-clipboard',
type:'splitbutton',
name:'paste',
text:'Paste',
iconCls:'icon-paste-large',
iconAlign:'top',
size:'large',
menuItems:[{
name:'paste',
text:'Paste',
disabled:true,
iconCls:'icon-paste'
},{
name:'paste-special',
text:'Paste Special...',
iconCls:'icon-paste'
}]
To enable or disable a menu item programmatically, get the menu object first and then call 'enableItem' or 'disableItem' methods to enable or disable the specified menu item. The code below shows how to enable the 'Paste' menu item.
var m = $('#btn-clipboard').splitbutton('options').menu; // get the menu object
var item = m.menu('findItem', 'Paste'); // find the menu item
m.menu('enableItem', item.target); // enable it