my -current is using Thunderbird 9x. And yesterday, somehow, I managed to screw the layout of it's Menu bar and Toolbar. The Menu bar should be on top, then below it the Toolbar. But by some magical keyboard shortcut I would never have known nor I can recall, I managed to swap the position between those 2 and leaving the Toolbar on top and below it, the Menu bar. It was ugly, dysfunctional and just plain wrong.
After a few misleading internet articles and forums regarding the issue, or nearly identical issues, I was left with the option of delete-and-test procedure. There's .thunderbird folder inside my $HOME and all the related settings is inside xxxxxxxx.default folder. Because there's a bunch of files, I deleted a subfolder inside then open up Thunderbird just to see did the layout was reverted back to normal. After nearly clearing the content of the .thunderbird folder, I found that the folder extensions is the one that I'm looking for.
So after I deleted the extensions folder, the layout reverted back to factory-default at the expense of losing my downloaded theme. Ah well that made me think that I can achieve the same result by changing theme to default and so it seems so. Better to lose the themes than lose my email settings. Later then.