In setting up Thunderbird on a new machine (I've used Thunderbird for years on other computers), I wanted to customize the Mail Toolbar with some icons I use frequently. I went to View, clicked on Toolbars, and then clicked on Customize. So far, so good. So then I tried to drag the trash can up, released my mouse button to drop it, and it was nowhere to be seen on the Mail Toolbar -- and it was no longer shown among the icons on the Customize Toolbar, so I couldn't try again. Clicking on Restore Default Set didn't bring it back among the icons available there. Nor did closing Thunderbird and then restarting Thunderbird. Ever the masochist, I tried to do all the same with the Reply icon, and encountered all the same problems. My question: Is there some way to get back all the icons in the Customize Set of icons when Restore Default Set doesn't work (though it does restore the unwanted icons I had earlier dragged off the Mail Toolbar)? If I could do that, I could try again to drag them up to the Mail Toolbar. Any advice would be much appreciated!