Вы можете сделать это, передав конфигурацию букв в конфигурацию indexBar
в списке:
Ext.setup({
onReady: function() {
var list = Ext.Viewport.add({
xtype: 'list',
itemTpl: '{name}',
grouped: true,
indexBar: {
letters: ['1', '2', '3']
},
store: {
grouper: {
groupFn: function(record) {
return record.get('series');
}
},
data: [
{ name: 'episode one', series: '1' },
{ name: 'episode two', series: '1' },
{ name: 'episode three', series: '1' },
{ name: 'episode one', series: '2' },
{ name: 'episode two', series: '2' },
{ name: 'episode one', series: '3' },
{ name: 'episode two', series: '3' },
{ name: 'episode three', series: '3' },
{ name: 'episode four', series: '3' }
]
}
});
}
});