None of the topics suggested fit. I'm having trouble with getting extensions on toolbars. In the customize toolbars window there's a toolbar at the very top of the page that starts with mail, calendar, addressbook, etc. Just for example, the Google Calendar and Outlook Calendar extensions are in that toolbar, but I can't move them to another toolbar and that toolbar disappears when I close the Customize page (either way) and I haven't been able to find a way to get it displayed in other places. That toolbar is very similar to the toolbar that appears on the left side of the Thunderbird window, but that one doesn't include the extra extension buttons that I mentioned above. Some people in various places have suggested that customizing Thunderbird toolbars is done the same way as in Firefox. But I haven't been able to find a puzzle piece icon anywhere. By the way, I used to be able to add more toolbars, which I found to be an attractive concept, although that implementation didn't always work so well.