for those just joining us, please see my post which (In my humble opinion) accurately summarizes the solution (that worked for me). Yes it requires installing two different programs (one of which is third party; one is from the good ol' MS app store) but such is the way it is until Windows overlords listen to their users and stop making horrible UX decisions.
EDIT: because this message board UX doesn't properly show the entire history of replies, here is the item I was responding to ("^this is the way") from user Emeskey on May 25, 2023 (couldnt find a way to link to it either - double shame on you MS for such a crappy message board platform!)
"If it's any help, I found an app in the Microsoft Store called "ModernFlyouts (Preview)" that allows you to customize the volume and brightness sliders, unfortunately it doesn't replace the current UI and also the app's slider can't be positioned vertically, but at least you can place it where you have better visibility on your screen.
Edit: I found a solution for the annoying current bottom-centered slider, there's an app called "HideVolumeOSD" that can get rid of it but doesn't interfere with the first app, you can find it here: HideVolumeOSD 1.4 for Windows 10 and 11 | Venturi.de."