Is there a simpler way of copying and pasting one inputs value into other input with the same name
One minor improvement I can think of is to create a variable to hold the input element since the element is used twice like

$(document).on('click', '.--copy', function () {
    var $input = $(this).closest('div').find('input'), input_name = $input.attr('name').split('-')[0];
    $('input[name^=' + input_name + ']').val($input.val());
});


Demo: Fiddle