One thing I missed the most from KDE was changing the volume by mouse wheel on the sound volume icon in tray. And in general mouse wheel interactions on tray.
On windows you have to click the icon before you can interact with it. IIRC on Mac too.
KDE has a lot of really nice little things, like how you can mute specific apps with a single click just like muting browser tabs.
I've used a variety of environments extensively (Windows, macOS, KDE, GNOME, Xfce, i3, dwm, you name it) and this is basically the one feature I find myself regularly missing from another environment.
On windows you have to click the icon before you can interact with it. IIRC on Mac too.