thunderbird missing arrows for scrolling through list of email messages

[charlie derr <charlie@emergencyguild.org>]

Greetings fine free software people.

A number of years ago, the little arrows at the top and bottom of the scrollbar to the right of my "message list" view in thunderbird (I'm currently using debian stable) disappeared. As I have a huge number of emails in my work inbox (not this account), this means that in order to "gradually" move backwards or forwards through the list of messages, I am forced to use mouse/trackpad/scrollwheel features (usually two fingers on my trackpad) as there is not enough "granularity" for me to pick up the scrollbar and move it (there's no way I can be accurate enough not to jump past many hundreds or even thousands of messages when I do this). 

I use KDE on one computer and Gnome Classic on others. Neither of these seems to provide for the "old school" arrows at the top and bottom of the scrollbar in the GUI which I can click on and hold (it used to be possible to do this and then have the messages scroll by at a speed which allowed me to notice what's going by and stop when i see a subject, recipient or sender that is relevant and so which I want to stop and open the message).

Any clue whether it's possible (by using a different window manager, configuring something in tbird, and/or by other means) to regain that older (and for me, very useful!) functionality, GUI-feature, or whatever the proper way to describe/categorize these widgets that disappeared might be?

    thanks so very very much in advance for any links to documentation, direction, guidance, advice, information, etc...
                ~c

P.S. CCs directly to me are fine (but I'll check the list for a few days too).