I found this;
function dokan_seller_displayname( $display_name ) {
if ( current_user_can( 'seller' ) && ! is_admin() ) {
$seller_info = dokan_get_store_info( dokan_get_current_user_id() );
$display_name = ( ! empty( $seller_info['store_name'] ) ) ? $seller_info['store_name'] : $display_name;
}
return $display_name;