There's probably some programs that you always want to run with the dedicated GPU, though.

Copy the launchers for those from /usr/share/applications to ~/.local/share/applications, and edit the Exec= line to include prime-run?

Or, assuming prime-run is inheritable (since otherwise apps that need renderer subprocesses wouldn't work), run an application launcher/menu itself with prime-run?

Actually, it looks like prime-run just sets a couple environment variables anyway. So set those however you want for each program.

What does "NVIDIA Control Panel" look like these days? It's been a couple years since I've seen it. No options in there?

I'm assuming you still want the IGPU and not the discrete GPU for rendering the desktop/simple programs, for power consumption and performance reasons, so you're not willing to just turn the IGPU off or stick your entire session under prime-run or export its environment variables in ~/.profile or whatever.

It looks like there are also GPU switcher taskbar applets for both KDE and GNOME. This sounds like it would be easy enough.

…I think back when I was setting up a NVIDIA laptop, I might have just put a toggle for optimus-manager somewhere, or something.