That is probably my biggest complaint in terms of "upgrades" they have done over the years as well.
It was very Microsoft-like how they non-nonchalantly took away the ability to configure that and just said, "well, they are up at the top now, you will have to get used to it".
Yes, that's why I freeze the software and versions I use whenever I can. I updated Windows 7 for the first time in five years this January. With Firefox I got tired of my bank's site telling my browser was out of date after a couple of years. So I upgraded and found out they broke my favorite theme and the customization I needed. I switched to Chrome but that is even worse in terms of customization.
I found some instructions to fix tabs and some other things so I upgraded Firefox again and fixed it up. Then one day it was all gone because of auto-update. They even may it hard to disable updates but it can be done with an enterprise policies file.
I am happy for now. I did notice a big improvement in site rendering and speed with the newer versions. I am currently on version 69.0.3 64bit. I was running version 22 until last year.
I have attached a summary of the key fixes. I also tweak additional config settings. These changes have only been tested on version 69. This document is only for reference - don't dive in unless yo are fearless - the web has lots of info.
This was the theme I used for many years - no longer usable. The cat with the ball wagged its tail while sites were loading.