View eMail reply to an inbox item

hi After you reply to a message in your inbox, a little left-facing arrow appears to the left of the subject, indicating that I replied to this message. In other email programs, when I click on that arrow, it will open up my reply email. When I click the arrow in Thunderbird, it simply disappears. Do I need an add-on or is there some setting I need to adjust? Life is much easier when that works! Thanks !