The search widget in the DataGrid is standard:
It really depends on your microflow, the search widget and all default controls of a data grid are programmed to work with objects and lists. Check your microflow and see what it returns or if it returns something, or post a screenshot of it so we can help you further.
Widget author here. You should put the DataGridColumnSearch widget below/after the data grid on the page in order for it to function properly. I realize that’s kind of odd and would love to address it in the future.