This hook-filter applies for any taxonomies terms in MDTF search forms. Use this hook in pair with https://wp-filter.com/features/mdf_terms_orderby/. Its callback can return 2 values only: 'ASC' or 'DESC'.
Example:
1 2 3 | add_filter('mdf_terms_order', function($default) { return 'DESC'; }); |
Read also: https://wp-filter.com/features/mdf_terms_orderby/