We just migrated our documentation to GitHub and we are doing our best to add any content that could be missing in the articles as soon as possible.
The missing client-side methods of the RadComboBox were added and will be live later today.
I am attaching a pdf file containing all the important RadComboBox, RadComboBoxItem and RadComboBoxItemCollection objects' methods in case you need them urgently.
As a token of gratitude for reporting this issue and your involvement I updated your Telerik points.
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