Hi,
duc01k@??? (2020-01-03):
> I noticed recently that there are no visible column dividers in the
> column headers in the main messages viewer window in Thunderbird. This
> makes it impossible to know where to click to resize the columns, you
> have to move the cursor across the headers until the cursor changes to
> the Resize cursor.
I can reproduce this outside of Tails. I don't know if it's
a conscious design decision in Thunderbird or GTK, or a bug.
Best would be to report this to Thunderbird upstream :)