There is probably a sub Reddit for these kinds of questions if you know of any.
Go to a sub of your choice. On the left side is a long list of subs you are subscribed to. The list is at the top of the alphabetically sorted groups. Now scroll down to one of your subs near the bottom of the list and click on it. The list should now stay at the bottom of the alphabet. That is the way it has always worked.
But starting yesterday the list resets to the top after I click on a new sub and I have to scroll down to where I want to be every time. I reset my computer and installed the latest Firefox update to no avail.