How to change panel icons only

I just upgraded to 24.04 and my panel icons are now different. I previously had modified a config file somewhere to change to panel icons to one theme, but keep the rest of the system with a different theme.
However I’ve since forgotten where this config file is. Can anyone point me in the right direction? I’m pretty sure it was somewhere in my home directory. There’s a good chance that when I upgraded the file was completely removed, so searching for it isn’t working.

You Can’t. Since plasma 6, panel will inherit the icons from the icon theme. The previous system was causing a lot of bugs.

Normally you can’t, but I’m referring to a workaround where you manually edit a config file that will indeed allow you to use more than one theme for different parts of the desktop environment.