I was getting the rightside toolbar in yahoo mail.
Yesterday I downloaded an update to the Apple IMac OS Big Sur OS,
and to Safari. Now I cannot get the rightside scrollbar in Yahoo mail.
(I still get the leftside toolbar).
(Apple was not able to help me, and told me to contact Yahoo.)
I was able to get the rightside scrollbar in Yahoo mail before downloading the Apple updates.
I am still able to get rightside scrollbars when in other websites, but not Yahoo mail.