I responded to your ticket about this problem but I will copy some of the information that I provided there in case other people come to this thread with the same problem.
When a ForeignKey column is used it internally assigns a values
). When the values
property is set to a column, the Grid automatically generates the DropDownList filter UI for the column and the custom filtering UI you try to assign is ignored.
It is possible to use the filterMenuInit
Grid event to empty the filtering container and add your custom UI, like shown in this KB: Create Filter Widgets with Multiple Filter Criteria in Grid
Anyway, when you want to have both custom filtering and editing UI, rather than that of the foreign key column, it would be easier to replace the ForeignKey column with a regular Bound column and use a ClientTemplate in the Bound column if needed to access the column text from outside the Grid data.