[рони]

tp-20,
...вариант

function down(id, h) {
        let margin_top = parseFloat($('#images-additional_wrapper').css('margin-top'));
        let max =
            parseFloat($('.images-additional').css('height')) -
            parseFloat($('#images-additional_wrapper').css('height'));
        if (margin_top - h < max) h = margin_top - max;
        $('#images-additional_wrapper').animate({
            'margin-top': '-=' + h + 'px',
        });
    }

    function up(id, h) {
        let margin_top = parseFloat($('#images-additional_wrapper').css('margin-top'));

        if (margin_top + h > 0) h = -margin_top;

        $('#images-additional_wrapper').animate({
            'margin-top': '+=' + h + 'px',
        });
    }