Use action hook wpda_before_list_table to add custom HTML and JavaScript before a list table. Argument $self contains a reference to your list table instance, which allows you to interact with your list table through public members and methods.
function mylisttable_elements( $self ) {
// Add you HTML and JavaScript here...
}
add_action( 'wpda_before_list_table', 'mylisttable_elements', 7 );