New fields for selecting custom sidebar(s) created via Genesis Simple Sidebars can be made to appear on custom taxonomy term edit forms in the WordPress backend by adding this code in child theme’s functions.php:
add_action( "{$tax}_edit_form", 'ss_term_sidebar', 9, 2 );
where {tax} is the id (internal name) of the custom taxonomy.
Ex.:
add_action( "class_type_edit_form", 'ss_term_sidebar', 9, 2 );