So I'd given one of my players the Rune Carver (now Rune Shaper) feat ages ago since we were running Storm King's Thunder and it fit with their backstory, however since it was all Unearthed Arcana at the time, I had to homebrew it on D&D Beyond and it was kind of Janky... They are also a Rune Knight, so I had homebrewed it to let the spells use their Consitution like the rest of their Runes. However now that the Rune Shaper feat is officially out, when I got to base a Homebrew off of it there are no options listed that I can adjust. The feat is basically just the description. I wanted to add Constitution to one of the options to be able to pick (And also boost it to being a number of spells = to their Prof Bonus, since that is also what they had been working with), but I can't find any way to change that... Any ideas? Is the code behind the feat to make it work just that different that it causes nothing to show up in the homebrew editor?

That stuff is all handled on the backend for feats and there’s no way to access it.