I suggest to create a hotkey, perhaps even a function key such as F6, to first of all move the "focus" to Thunderbird, and within Thunderbird to further move the "focus" to the preview of the currently selected email, and also to automatically scroll to the bottom of said email, and if possible to hover the mouse over the Unsubscribe button.
Some of us get a lot of junk mail, and we try to keep on top of it by Unsubscribing from each junk mail, but yet more junk mail comes and so it's never-ending. Filtering works for some junk mails, but many junk mails slip through the cracks, and unsubscribing seems easier sometimes than creating a new filter. However, even unsubscribing takes numerous mouse moves and mouse clicks, and it becomes even more cumbersome if you have 50 emails to go through daily.
A hotkey to automatically move the cursor to hover over the "Unsubscribe" button at the bottom of an email (in the preview pane) would be a godsend.
So unsubscribing from 50 emails would go something like this:
Press F6 {mouse hovers over "unsubscribe" at the bottom of email in the preview pane}
Left-click the mouse (No need to move the mouse!) to unsubscribe from current email (browser pops up and "focus" moves to browser)
Press Alt-Tab to return the "focus" to Thunderbird
Press Delete to delete said email.
Repeat these four steps until your list is depleted. (It would be very quick!!)