URLs menu example for Custom Buttons https://addons.mozilla.org/addon/custom-buttons/

cbMenuURLs.js

// https://gist.github.com/Infocatcher/6484572
// Based on https://gist.github.com/Infocatcher/5891622

var options = {
	showTooltips: true,
	openInBackground: false
};

var menu = [
	// cb_url:
	//   %URL%     - encodeURIComponent(content.location.href)
	//   %RAW_URL% - content.location.href
	{ label: "Search in Google Cache", cb_url: "https://www.google.com/search?q=cache:%URL%", image: "https://www.google.com/favicon.ico" },
	{ label: "Search in web.archive.org", cb_url: "http://web.archive.org/web/*/%RAW_URL%", image: "http://archive.org/images/glogo.jpg" },
	{ label: "View over anonymouse.org", cb_url: "http://anonymouse.org/cgi-bin/anon-www.cgi/%RAW_URL%", image: "http://anonymouse.org/favicon.ico" },
	"menuseparator",
	{ label: "View page source", cb_url: "view-source:%RAW_URL%" },
	"menuseparator",
	[
		"Menu label",
		"https://www.google.com/favicon.ico",
		{ label: "Sub item 1", cb_url: "https://www.google.com/" },
		{ label: "Sub item 2", cb_url: "http://www.yandex.ru/" }
	],
	[
		"Menu label 2",
		{ label: "Sub item 3", cb_url: "http://nigma.ru/" },
		{ label: "Sub item 4", cb_url: "http://www.bing.com/" }
	]
];

function getURLs(url) {
	// Simplified example!
	var out = [];
	if(/#/.test(url))
		out.push((url = RegExp.leftContext));
	if(/\?/.test(url))
		out.push((url = RegExp.leftContext));
	var protocol = "";
	if(/^[^\/:]+:\/*/.test(url)) {
		protocol = RegExp.lastMatch;
		url = RegExp.rightContext;
		//LOG("protocol: " + protocol);
	}
	url = url.replace(/\/+$/, "");
	while(/\/[^\/]+$/.test(url)) {
		url = RegExp.leftContext;
		if(!url)
			break;
		out.push(protocol + url + "/");
	}
	return out;
}

function parseItem(arr, parent) {
	if(!parent)
		parent = document.createElement("menupopup");
	arr.forEach(function(item) {
		var node;
		if(item == "menuseparator")
			node = document.createElement("menuseparator");
		else if(Array.isArray(item)) {
			node = document.createElement("menu");
			node.setAttribute("label", item[0]);
			var icon = item[1];
			if(typeof icon == "string") {
				node.className = "menu-iconic";
				node.setAttribute("image", icon);
			}
			else {
				node.className = "menu-iconic bookmark-item";
				node.setAttribute("container", "true");
			}
			var mp = document.createElement("menupopup");
			parseItem(item, mp);
			node.appendChild(mp);
		}
		else if(typeof item == "object" && item) {
			node = document.createElement("menuitem");
			if(/*item.hasOwnProperty("image") && */!item.hasOwnProperty("class"))
				item.class = "menuitem-iconic bookmark-item menuitem-with-favicon";
			for(var attr in item) if(item.hasOwnProperty(attr))
				node.setAttribute(attr, item[attr]);
		}
		node && parent.appendChild(node);
	});
	return parent;
}

var mp = document.createElement("menupopup");
var firstStaticItem;
mp.setAttribute("onpopupshowing", "if(event.target == this) this.parentNode.buildMenu(this);");
mp.setAttribute("oncommand", "this.parentNode.handleCommand(event);");
mp.setAttribute("onclick", "if(event.button != 0) this.parentNode.handleCommand(event);");
mp.setAttribute("oncontextmenu", "return false;");
addEventListener("DOMMenuItemActive", showLink, false, mp);
addEventListener("DOMMenuItemInactive", showLink, false, mp);

this.type = "menu";
this.orient = "horizontal";
this.appendChild(mp);

function showLink(e) {
	if(e.type == "DOMMenuItemActive") {
		var mi = e.target;
		var url = getURL(mi.getAttribute("cb_url") || "");
		if(url && options.showTooltips && mi.getAttribute("tooltiptext") != url)
			mi.setAttribute("tooltiptext", url);
		XULBrowserWindow.setOverLink(url, null);
	}
	else if(e.type == "DOMMenuItemInactive") {
		XULBrowserWindow.setOverLink("", null);
	}
}
this.buildMenu = function(popup) {
	if(!firstStaticItem) {
		parseItem(menu, popup);
		firstStaticItem = mp.firstChild;
	}
	for(var node; (node = popup.firstChild) && node != firstStaticItem;)
		popup.removeChild(node);
	var df = document.createDocumentFragment();
	getURLs(content.location.href).forEach(function(url) {
		if(url == "menuseparator") {
			df.appendChild(document.createElement("menuseparator"));
			return;
		}
		var mi = document.createElement("menuitem");
		mi.setAttribute("label", url);
		mi.setAttribute("cb_url", url);
		mi.className = "menuitem-iconic bookmark-item menuitem-with-favicon";
		df.appendChild(mi);
	});
	if(df.hasChildNodes())
		df.appendChild(document.createElement("menuseparator"));
	mp.insertBefore(df, firstStaticItem);
};
this.handleCommand = function(e) {
	var trg = e.target;
	var url = trg.getAttribute("cb_url");
	if(!url)
		return;
	var btn = e.type == "click" && e.button || 0;
	if(btn == 2)
		return;
	btn && closeMenus(trg); // See chrome://browser/content/utilityOverlay.js
	//alert("Button: " + btn + "\nURL: " + url);

	url = getURL(url);
	if(btn > 0 || e.ctrlKey || e.shiftKey || e.altKey || e.metaKey) {
		var tab = gBrowser.addTab(url);
		if(options.openInBackground)
			gBrowser.selectedTab = tab;
	}
	else {
		loadURI(url);
	}
};

function getURL(template) {
	var curURL = content.location.href;
	return template
		.replace(/%URL%/g, encodeURIComponent(curURL))
		.replace(/%RAW_URL%/g, curURL);
}