Currently, in RadMultiColumnComboBox, if you AutoFilter by all columns and you type a value that resides in the ID column, while the DisplayMember is the Name, pressing the Enter after typing the ID will return the Name in the textbox part which may be confusing to the user. Such a case may be solved by introducing another textbox in the drop-down part just for filtering purposes.

Currently RadMultiColumnComboBox uses exact comparison and it is not possible to change this behavior.

When you enable the popup sizing functionality, the last user defined size by the sizing grip should be kept.