Hi Erik,
The Kendo UI MultiSelect will show the value of the group in the labels by default as outlined at:
http://docs.telerik.com/kendo-ui/api/javascript/ui/multiselect#configuration-groupTemplate
No other information is available, therefore, you cannot access other fields of the Kendo UI Data Source. To group the items in a different order other than the supported options - ascending/descending, then you should do the custom grouping on the server and enable serverGrouping:
http://docs.telerik.com/kendo-ui/api/javascript/data/datasource#configuration-serverGrouping
Alternatively, if you would like to keep your implementation the way it is at the moment, you may create an object with properties (key-value pairs) to act as a switch case in the Kendo UI Template. The property name could be the genuine field which the Kendo UI Data Source is grouped by (i.e the data) and the value should be the custom label you require.
For your convenience, I have prepared a runnable demo at:
http://dojo.telerik.com/obInO
Regards,
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Telerik by Progress
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