I've successfully added a relationship (show as admin column option) to the custom post type admin page.
The column is visible but I can't sort my result based on this column (sortable / filtrable). How can I add this functionality ?
I'm using Admin Columns Pro but the "order / sort / filter" option is not available for this type of column.
Currently, MB Admin Columns does not support sorting by relationship values. And please note that the sort parameter is used to sort displayed posts by altering the WordPress query. It works only with non-clonable and non-multiple fields.