Hi Fie,
Thanks for your interest in syncfusion products.
In ComboboxAutoComplete there is no support for multisuggestextended. We have created a workaround to achieve your requirement which is available in the below link.
Sample:http://www.syncfusion.com/downloads/Support/DirectTrac/110470/combomultiextend-1138691954.zip
Please have the sample and let us know if you have any concerns.
Regards,
Paul Anderson S