windows 11 and some V10 use the hidden and much reduced scrollbars as a part of the operating system changes. You appear to be using a theme. Perhaps that is the issue. Restart Thunderbird from the help menu in troubleshoot mode and see if things look different in that mode to what you are seeing now.

I did what you said but it didn't help. I did wonder if it was my windows 10 causing it. I have the following:

Edition Windows 10 Pro Version 22H2 Installed on ‎22/‎08/‎2020 OS build 19045.4046 Experience Windows Feature Experience Pack 120.2212.3920.0

Perhaps I should be looking in Windows 10 forums for a solution. Maybe there wont be one.  :(

Thanks for your suggestion anyway. I've decided to permanently get rid of addons and themes to make sure any future updates of Thunderbird aren't hindered by it.

I'm using Windows 10 and beta 124.0b1 so I just checked 'Cards View' which I do not normally use.

I also see a scrollbar even though it does not actually have the moveable scrollbar section because the list is too short and does not require any scrollbar.

So you are not unique.

However, I also see in the 'Table View' as well and the View > Layout options Classic or Vertical have no effect on outcome.

I'm using the Thunderbird dark theme.

I do not think this has anything to do with the OS because running version 102.15.1 does not display this issue. So it's got to something in the new 115* code.

I've created a bug report for this issue: https://bugzilla.mozilla.org/show_bug.cgi?id=1883041

Thank you Toad-Hall.