Grouping combobox list values helps to systematize the items. This feature is already available in ‘Ext.grid.Panel’ but unfortunately not available for ‘Ext.form.field.ComboBox’. To implement the field as a single class I have changed the ‘Ext.view.BoundList’ throw ‘Ext.form.field.ComboBox:listConfig’ configuration property.

Group combobox store must be configured with ‘groupField‘ property. You also need to create new similar to ‘.x-boundlist-item’ ‘.x-boundlist-group-item’ CSS class in case of Triton theme. To change the layout of Group item you will have to change the ‘GroupComboBox:getGroupInnerTpl()’ method. For example:

In the following fiddle sample of the GroupComboBox I have loaded store with 5976 elements to check the performance of the GUI element. Works for ExtJS 6.2 and 6.5 versions.