I'm trying to find a way to better keep track of a homebrew spell ability granted by a custom background that I made. The issue is that it seems that DDB doesn't allow for additional cantrips to be known for a character, regardless of whether it's a standard spell already available.

Is there any way to modify the number of cantrips known within DDB? I have a newer player in my game and if the cantrips aren't in the Spells section of their char sheet then I'm afraid they'll be forgotten without a constant reminder. They're cantrips, and not game-breaking, but they are great for the role-playing and character development I'm hoping to help them develop.

Sure, you can add cantrips via a feature. You cannot increase the number of “Cantrips Known,” but you can certainly add cantrips to the character, and even give them a choice of cantrips. Please see the Homebrewed Subclasses & Species FAQ #s 14 & 15: (https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/131411-a-homebrewers-how-to-faq). It’s close enough to the way feats are set up to at least get you where you need, and if you need more help just ask.

Thanks. I also found a Reddit post about using or modifying the Innate Spellcaster feat for the particular class I needed that allowed for the cantrips to be added as known spells, so I just used that as a template and modified it to accomplish what I wanted for the Homebrew feat I wanted to add. 

Yeah, that’s gonna achieve the same end result.