The reset button is used to apply firmware changes. For this keyboard you can customize the keys to pretty much however you like. I have one of the thumb cluster buttons set to Ctrl-C / Ctrl-V for efficiency. It’s great for making changes to personalize your mechanical keyboard experience… but it requires that pin to make changes lol.
I like it since I can assign Enter to one of the left thumb cluster buttons, you normally can’t hit enter with your left hand on a standard keyboard layout.