There is no "toggling".
When you boot up a computer, it first activates the hardware, from there the BIOS (the firmware/os of the motherboard) activates to then start activating all the hardware's connectivity and capabilities.
From here it then looks for a storage device to boot an OS from.
Once you pass the BIOS splash screen you you are no longer at BIOS level on the system and therefore cannot boot into it's firmware to adjust settings.
There are plenty of in depth technical reasons why you can't just swap to the BIOS environment right from within Windows and swap right back as if nothing ever happened, but that would be an essay all in itself and I'm not gonna do that here lol.
To keep it short, no. There is no toggle.
You have to boot into the BIOS at startup during the splash screen.
If overclocking a CPU and looking to adjust settings for that, try using the Ryzen Master software.
Otherwise, you have to do it the long, tedious, and old fashioned way like the rest of us and restart your PC and go into the BIOS every time you want to change something.