its the custom firmware that does it, the layout and layers I just made up as I needed them but its flashing the firmware every time I want to change something. There are other keyboards and keyboard firmwares that can do this, I use qmk, and its possible to mod normal keyboards to varying difficulty. The keyboard I have is a semi diy that came as a kit but there are others ready to use but still customizable in firmware. I think there was also another kb firmware that let you live edit the layouts without flashing firmware using a config software but I haven’t looked in to it.

Links to the firmware+keyboard. https://docs.qmk.fm/ https://olkb.com/

I have an fn1 and fn2 key on my preonic and holding fn1 replaces qwer,asdf,zxcv with f1-4,f5-8,f9-12 and fn2 does f13-24 in the same positions. some games have been able to map things to them but the glyphs tend to not work, but mostly I use them for global shortcuts like turning on or off the mobo LEDs, multi monitor layout presets, etc