Delete all items, in https://prntscr.com/gallery.html history page.

delete-all-lightshot-app-gallery-history-items.js

var intervalHandle = setInterval(function() {
    var i = 0;
    $('.js-delete').each(function() {
        if (i > 5) {
            return false;
        }
        $(this).click();
        if ($(this).parent().css('display') == 'block') {
            i++;
        }

    });
    // Confirm delete forever
    $('.js-delete-forever').each(function() {
        if ($(this).parent().css('display') == 'block') {
            $(this).click();
        }
    });
    if ($('.js-delete').lengh == 0) {
        clearInterval(intervalHandle);
    }
}, 2000);