Change melee attack bonus?

I may just be showing my relative noob-ness, and if so I do apologize, but is there a way to change the melee attack bonus on the character sheet? I've made a custom class feature to allow a character to base their attack off their DEX mod instead of their STR mod, and it doesn't look like there is a way to edit what the bonus is without changing the Ability Score.

So as its coded you cannot. I could unlock that box but its going to update every time you change your strength score or restart the game/open the character sheet. I scripted it based on RAW and have been adding optional rules. I did not see this as an optional rule. What edition started allowing dex to be used for some weapon attacks?