Switch to using objects instead of arrays for each entry in afeeds[]. That is, instead of afeeds[url-of-open-tab] = [ [title1, feed-url1], [title2, feed-url2]…], we now have afeeds[url] = {feed-url1:title1, feed-url2:title2, …}.

This makes it a bit easier to add feeds to a page's menu asynchronously, as there's a neat jQuery function ($.extend) that merges the properties of one object into another.