Hi Pete,
Thank you for your interest in Syncfusion Products.
We have notified the respective team about the missing ClassReference and we will get that fixed in the future releases. I am afraid that I am not able to see your issue of the multicolumn dropdown documentation is missing.You can find more details on using the MultiColumnDropdown combo in the online documentation link below.
http://help.syncfusion.com/ug_82/ASP.NETUI_Tools/Tutorial10.htmlKindly try the above and please let me know if any concerns.
Regards,
Lakxman Kumar C