How to do Multi select Pick in TFS workitem field control?

Hi,

     I am creating one custom work item and need one multi select field control for “Supported Products” . Current I have to write all combination in the List “Allowed values” .This looks not smart.

May I just list O12,O14,O15  and do multi select ?  Or Is there has other solution?

I have try hold ctrl or shift , but can't select multi values.

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