A Greasemonkey plugin that allows you to define combined WIP limits for columns on your Jira Agile board (f.k.a. RapidBoard). To group columns, the first word of the column name is used.

de.mobile.rapidboard.combinedlimits.user.js

// ==UserScript==
// @name Jira Rapid Board combined limits
// @namespace Jira
// @include https://jira.corp.mobile.de/jira/secure/RapidBoard.jspa*
// @version 4
// @grant none
// ==/UserScript==
(function jiraRapidBoardCombinedLimits($) {

    function refreshLimits() {
        var groups = {};
        var classesForColumns = {};
        var $header = $('ul#ghx-column-headers');
        $header.find('li.ghx-column').each(function() {
            min = 0;
            var $column = $(this);
            $column.removeClass("ghx-busted ghx-busted-max");
            var groupKey = $column.children('h2').text().split(/ /)[0];
            var min = parseInt($('.ghx-limits .ghx-busted-min', $column).text().replace(/Min[^ ]* /, ""));
            var max = parseInt($('.ghx-limits .ghx-busted-max', $column).text().replace(/Max[^ ]* /, ""));
            var current = parseInt($('.ghx-qty', $column).text());

            if (!groups[groupKey]) {
                groups[groupKey] = {
                    $columns: $(),
                    current: 0
                };
            }

            var group = groups[groupKey];
            group.$columns = group.$columns.add($column);
            if (min) group.min = group.min ? group.min + min : min;
            if (max) group.max = group.max ? group.max + max : max;
            group.current = group.current + current;
        });

        for (var groupKey in groups) {
            var group = groups[groupKey];

            var $limit = $('<div class="ghx-x-limit-combined"></div>');
            if (group.current && group.max) {
                $limit.text('Combined: ' + group.current + ' of ' + group.max);

                var addClass = null;
                if (group.current == group.max) addClass = 'ghx-x-limit-warning';
                if (group.current > group.max) addClass = 'ghx-x-limit-fail';

                group.$columns.each(function() {
                    classesForColumns[$(this).data().id] = addClass;
                });
            }

            group.$columns.children('.ghx-x-limit-combined').remove();
            group.$columns.append($limit);
        }

        $('#ghx-pool .ghx-swimlane .ghx-column').each(function() {
            var $cell = $(this);
            group.$columns.removeClass("ghx-x-limit-warning ghx-x-limit-fail");
            $cell.addClass(classesForColumns[$cell.data().columnId]).removeClass("ghx-busted ghx-busted-max");
        });
    }

    $(function() {
        var css = ".ghx-column.ghx-x-limit-warning { background-color: gold; } " + ".ghx-column.ghx-x-limit-fail { background-color: crimson; } " + ".ghx-x-limit-combined { position: absolute; bottom: 0; font-size: 11px; color: #707070 }";
        $('head').append($('<style></style>').html(css))

        refreshLimits();

        var handlerActive = false;
        $("#ghx-pool").live("DOMNodeInserted", function(event) {
            var $this = $(event.target);
            if ($this.closest('#ghx-column-header-group').length > 0 && !handlerActive) {
                handlerActive = true;
                refreshLimits();
                handlerActive = false;
            }
        });

    });

}(jQuery));

You can use my plugin to do the same: https://jirasupport.wordpress.com/2016/01/13/start-this-year-with-two-free-awesome-plugins-for-your-jira-6-or-7/