I use Thunderbird 45.1.1 with Windows 10. I run Thunderbird from the Taskbar; the icon is in the left. Up until a couple of days ago, when I ran Thunderbird, it put another icon (with a line underneath it) at the right end of the Taskbar. I would leave Thunderbird open all day, and if I ran something else, I would bring Thunderbird up by clicking on that, second, icon. Thunderbird was the only program that made a second icon. Now, it doesn't put an additional icon at the right. It does put the line underneath the Taskbar icon at the left. Does this matter?