here is my code: list_filter = (('question_id',DropdownFilter),('question',DropdownFilter),('qtype',RelatedDropdownFilter), ('difficulties',RelatedDropdownFilter),('subject',RelatedDropdownFilter), ('topic',RelatedDropdownFilter),('sub_topic',RelatedDropdownFilter))
It's not showing because there are too little values in your choices, dropdowns are rendered if the choices list contains more than 4 values, see here. Can you send a pull request to document this?
here is my code:
list_filter = (('question_id',DropdownFilter),('question',DropdownFilter),('qtype',RelatedDropdownFilter), ('difficulties',RelatedDropdownFilter),('subject',RelatedDropdownFilter), ('topic',RelatedDropdownFilter),('sub_topic',RelatedDropdownFilter))
here is the screenshot: